From cddfcce490dd3273a45ad6e1009d36b4cb6c5b37 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 11:20:11 +0200
Subject: [PATCH 01/26] Changed: Introduced relations in OT.

---
 src/model/operation/transform.js             | 303 ++++++++++++++++---
 src/model/position.js                        |   1 +
 tests/model/operation/transform.js           |  42 +--
 tests/model/operation/transform/attribute.js |   2 +-
 tests/model/operation/transform/insert.js    |   4 +-
 tests/model/operation/transform/marker.js    |   4 +-
 tests/model/operation/transform/move.js      |   8 +-
 tests/model/operation/transform/remove.js    |  12 +-
 tests/model/operation/transform/split.js     |  27 +-
 tests/model/operation/transform/unwrap.js    |   5 +-
 tests/model/operation/transform/utils.js     |  42 ++-
 tests/model/operation/transform/wrap.js      |  52 +++-
 12 files changed, 377 insertions(+), 125 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index f0a9dba73..ee05eee28 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -72,7 +72,7 @@ function updateBaseVersions( operations, baseVersion ) {
 	return operations;
 }
 
-function transform( a, b, context = { aIsStrong: false } ) {
+function transform( a, b, context = { aIsStrong: false, wasUndone: () => false, getRelation: () => null } ) {
 	const transformationFunction = getTransformation( a, b );
 
 	return transformationFunction( a.clone(), b, context );
@@ -124,6 +124,8 @@ function transformSets( operationsA, operationsB, options ) {
 					if ( options.useContext ) {
 						updateOriginalOperation( context, opA, newOpA );
 						updateOriginalOperation( context, opB, newOpB );
+
+						updateRelations( context, opA, opB );
 					}
 
 					opsA.splice( k, 1, ...newOpA );
@@ -176,6 +178,7 @@ function initializeContext( opsA, opsB, options ) {
 	}
 
 	context.document = options.document;
+	context.relations = new Map();
 
 	context.wasUndone = function( op ) {
 		if ( !options.useContext ) {
@@ -187,9 +190,151 @@ function initializeContext( opsA, opsB, options ) {
 		return this.document.history.isUndoneOperation( originalOp );
 	};
 
+	context.getRelation = function( opA, opB ) {
+		if ( !options.useContext ) {
+			return null;
+		}
+
+		const origB = this.originalOperations.get( opB );
+		const undoneB = this.document.history.getUndoneOperation( origB );
+
+		if ( !undoneB ) {
+			return null;
+		}
+
+		const origA = this.originalOperations.get( opA );
+		const relationsA = this.relations.get( origA );
+
+		if ( relationsA ) {
+			return relationsA.get( undoneB ) || null;
+		}
+
+		return null;
+	};
+
 	return context;
 }
 
+function updateRelations( context, opA, opB ) {
+	switch ( opA.constructor ) {
+		case MoveOperation:
+		case RemoveOperation:
+		case ReinsertOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.targetPosition.isEqual( opB.sourcePosition ) || opB.movedRange.containsPosition( opA.targetPosition ) ) {
+						setRelation( context, opA, opB, 'insertAtSource' );
+						setRelation( context, opB, opA, 'splitBefore' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.targetPosition.isEqual( opB.sourcePosition ) || opA.targetPosition.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'insertBefore' );
+						setRelation( context, opB, opA, 'insertAfter' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.targetPosition.hasSameParentAs( opB.targetPosition );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'insertInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+
+		case SplitOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'splitBefore' );
+						setRelation( context, opB, opA, 'splitAfter' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'splitBefore' );
+						setRelation( context, opB, opA, 'insertAtSource' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.position.hasSameParentAs( opB.position );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'splitInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+
+		case InsertOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opB.movedRange.containsPosition( opA.position ) ) {
+						setRelation( context, opA, opB, 'insertAtSource' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'insertBefore' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.position.hasSameParentAs( opB.position );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'insertInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+	}
+}
+
+function setRelation( context, opA, opB, relation ) {
+	const origA = context.originalOperations.get( opA );
+	const origB = context.originalOperations.get( opB );
+
+	let relationsA = context.relations.get( origA );
+
+	if ( !relationsA ) {
+		relationsA = new Map();
+		context.relations.set( origA, relationsA );
+	}
+
+	relationsA.set( origB, relation );
+}
+
 function updateOriginalOperation( context, oldOp, newOps ) {
 	const originalOp = context.originalOperations.get( oldOp );
 
@@ -345,8 +490,12 @@ setTransformation( AttributeOperation, MergeOperation, ( a, b ) => {
 
 	// Case 1:	Attribute change on the merged element. In this case, the merged element was moved to graveyard.
 	//			An additional attribute operation that will change the (re)moved element needs to be generated.
+	//			Do it only, if there is more than one element in attribute range. If there is only one element,
+	//			it will be handled by the default algorithm.
 	//
-	if ( a.range.start.hasSameParentAs( b.deletionPosition ) ) {
+	const howMany = a.range.end.offset - a.range.start.offset;
+
+	if ( howMany > 1 && a.range.start.hasSameParentAs( b.deletionPosition ) ) {
 		if ( a.range.containsPosition( b.deletionPosition ) || a.range.start.isEqual( b.deletionPosition ) ) {
 			ranges.push( Range.createFromPositionAndShift( b.graveyardPosition, 1 ) );
 		}
@@ -541,13 +690,23 @@ setTransformation( InsertOperation, InsertOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, MoveOperation, ( a, b ) => {
+setTransformation( InsertOperation, MoveOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'insertBefore' ) {
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByMoveOperation( b );
 
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, SplitOperation, ( a, b ) => {
+setTransformation( InsertOperation, SplitOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+		a.position = b.moveTargetPosition;
+
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedBySplitOperation( b );
 
 	return [ a ];
@@ -559,7 +718,13 @@ setTransformation( InsertOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, WrapOperation, ( a, b ) => {
+setTransformation( InsertOperation, WrapOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+		a.position = b.targetPosition;
+
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByWrapOperation( b );
 
 	return [ a ];
@@ -716,7 +881,7 @@ setTransformation( MergeOperation, MoveOperation, ( a, b, context ) => {
 	a.sourcePosition = a.sourcePosition._getTransformedByMoveOperation( b );
 	a.targetPosition = a.targetPosition._getTransformedByMoveOperation( b );
 
-	if ( !a.graveyardPosition.isEqual( b.targetPosition ) || !context.aIsStrong ) {
+	if ( !a.graveyardPosition.isEqual( b.targetPosition ) ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
@@ -747,9 +912,9 @@ setTransformation( MergeOperation, SplitOperation, ( a, b ) => {
 	//			There is one exception though - when the split operation is a result of undo. In those cases, it is needed
 	//			to keep `targetPosition` intact, so the nodes are returned to the correct element.
 	//
-	if ( a.targetPosition.isEqual( b.position ) && b.graveyardPosition ) {
-		return [ a ];
-	}
+	// if ( a.targetPosition.isEqual( b.position ) && b.graveyardPosition ) {
+	// 	return [ a ];
+	// }
 
 	a.targetPosition = a.targetPosition._getTransformedBySplitOperation( b );
 
@@ -814,14 +979,14 @@ setTransformation( MergeOperation, UnwrapOperation, ( a, b, context ) => {
 
 // -----------------------
 
-setTransformation( MoveOperation, InsertOperation, ( a, b ) => {
+setTransformation( MoveOperation, InsertOperation, ( a, b, context ) => {
 	const moveRange = Range.createFromPositionAndShift( a.sourcePosition, a.howMany );
 	const transformed = moveRange._getTransformedByInsertOperation( b, false )[ 0 ];
 
 	a.sourcePosition = transformed.start;
 	a.howMany = transformed.end.offset - transformed.start.offset;
 
-	if ( !a.targetPosition.isEqual( b.position ) ) {
+	if ( !a.targetPosition.isEqual( b.position ) || context.getRelation( b, a ) == 'insertBefore' ) {
 		a.targetPosition = a.targetPosition._getTransformedByInsertOperation( b );
 	}
 
@@ -838,14 +1003,23 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 
 	// Assign `context.aIsStrong` to a different variable, because the value may change during execution of
 	// this algorithm and we do not want to override original `context.aIsStrong` that will be used in later transformations.
-	let aIsStrong = context.aIsStrong;
+	let aIsStrong = context.aIsStrong || context.getRelation( a, b ) == 'insertBefore';
 
 	// `a.targetPosition` could be affected by the `b` operation. We will transform it.
-	const newTargetPosition = a.targetPosition._getTransformedByMove(
-		b.sourcePosition,
-		b.targetPosition,
-		b.howMany
-	);
+	let newTargetPosition;
+
+	if ( a.targetPosition.isEqual( b.targetPosition ) && aIsStrong ) {
+		newTargetPosition = a.targetPosition._getTransformedByDeletion(
+			b.sourcePosition,
+			b.howMany
+		);
+	} else {
+		newTargetPosition = a.targetPosition._getTransformedByMove(
+			b.sourcePosition,
+			b.targetPosition,
+			b.howMany
+		);
+	}
 
 	//
 	// Special case #1 + mirror.
@@ -993,7 +1167,7 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 	return makeMoveOperationsFromRanges( ranges, newTargetPosition );
 } );
 
-setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
+setTransformation( MoveOperation, SplitOperation, ( a, b, context ) => {
 	const newTargetPosition = a.targetPosition._getTransformedBySplitOperation( b );
 
 	// Case 1:	Last element in the moved range got split.
@@ -1028,8 +1202,8 @@ setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
 		rightRange = rightRange._getTransformedBySplitOperation( b );
 
 		const ranges = [
-			rightRange,
-			Range.createFromPositionAndShift( moveRange.start, b.position.offset - moveRange.start.offset )
+			new Range( moveRange.start, b.position ),
+			rightRange
 		];
 
 		return makeMoveOperationsFromRanges( ranges, newTargetPosition );
@@ -1043,6 +1217,10 @@ setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
+	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+		a.targetPosition = b.targetPosition;
+	}
+
 	return [ a ];
 } );
 
@@ -1081,7 +1259,7 @@ setTransformation( MoveOperation, MergeOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( MoveOperation, WrapOperation, ( a, b ) => {
+setTransformation( MoveOperation, WrapOperation, ( a, b, context ) => {
 	const moveRange = Range.createFromPositionAndShift( a.sourcePosition, a.howMany );
 	const newTargetPosition = a.targetPosition._getTransformedByWrapOperation( b );
 
@@ -1133,6 +1311,10 @@ setTransformation( MoveOperation, WrapOperation, ( a, b ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
+	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+		a.targetPosition = b.targetPosition;
+	}
+
 	return [ a ];
 } );
 
@@ -1235,7 +1417,11 @@ setTransformation( RootAttributeOperation, RootAttributeOperation, ( a, b, conte
 
 // -----------------------
 
-setTransformation( SplitOperation, InsertOperation, ( a, b ) => {
+setTransformation( SplitOperation, InsertOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertAtSource' ) {
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByInsertOperation( b );
 
 	return [ a ];
@@ -1251,7 +1437,7 @@ setTransformation( SplitOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
+setTransformation( SplitOperation, MoveOperation, ( a, b, context ) => {
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
@@ -1279,6 +1465,12 @@ setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
 		return [ a ];
 	}
 
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+		a.position = a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
+
+		return [ a ];
+	}
+
 	// The default case.
 	//
 	a.position = a.position._getTransformedByMoveOperation( b );
@@ -1286,7 +1478,7 @@ setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
+setTransformation( SplitOperation, SplitOperation, ( a, b, context ) => {
 	if ( a.position.isEqual( b.position ) ) {
 		if ( !a.graveyardPosition && !b.graveyardPosition ) {
 			return getNoOp();
@@ -1295,6 +1487,8 @@ setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
 		if ( a.graveyardPosition && b.graveyardPosition && a.graveyardPosition.isEqual( b.graveyardPosition ) ) {
 			return getNoOp();
 		}
+	} else if ( a.position.isEqual( b.insertionPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+		return [ a ];
 	} else {
 		a.position = a.position._getTransformedBySplitOperation( b );
 	}
@@ -1306,7 +1500,7 @@ setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
+setTransformation( SplitOperation, WrapOperation, ( a, b, context ) => {
 	// Case 1:	If split position has been wrapped, reverse the wrapping so that split can be applied as intended.
 	//			This is an edge case scenario where it is difficult to find a correct solution.
 	//			Since it will be a rare (or only theoretical) scenario, the algorithm will perform the easy solution.
@@ -1324,7 +1518,11 @@ setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
 		return [ reversed, a ];
 	}
 
-	a.position = a.position._getTransformedByWrapOperation( b );
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'splitInside' ) {
+		a.position = b.targetPosition;
+	} else {
+		a.position = a.position._getTransformedByWrapOperation( b );
+	}
 
 	if ( a.graveyardPosition && b.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByDeletion( b.graveyardPosition, 1 );
@@ -1333,8 +1531,17 @@ setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, UnwrapOperation, ( a, b ) => {
-	a.position = a.position._getTransformedByUnwrapOperation( b );
+setTransformation( SplitOperation, UnwrapOperation, ( a, b, context ) => {
+	const splitInside = a.position.hasSameParentAs( b.position );
+
+	if ( splitInside && !context.wasUndone( b ) ) {
+		const path = b.graveyardPosition.path.slice();
+		path.push( 0 );
+
+		a.position = new Position( b.graveyardPosition.root, path );
+	} else {
+		a.position = a.position._getTransformedByUnwrapOperation( b );
+	}
 
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByInsertion( b.graveyardPosition, 1 );
@@ -1345,7 +1552,13 @@ setTransformation( SplitOperation, UnwrapOperation, ( a, b ) => {
 
 // -----------------------
 
-setTransformation( WrapOperation, InsertOperation, ( a, b ) => {
+setTransformation( WrapOperation, InsertOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertInside' ) {
+		a.howMany += b.howMany;
+
+		return [ a ];
+	}
+
 	const transformed = a.wrappedRange._getTransformedByInsertOperation( b, false )[ 0 ];
 
 	a.position = transformed.start;
@@ -1367,11 +1580,18 @@ setTransformation( WrapOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( WrapOperation, MoveOperation, ( a, b ) => {
+setTransformation( WrapOperation, MoveOperation, ( a, b, context ) => {
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( b, a ) == 'insertInside' ) {
+		a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
+		a.howMany += b.howMany;
+
+		return [ a ];
+	}
+
 	const ranges = breakRangeByMoveOperation( a.wrappedRange, b, false );
 
 	if ( ranges.length == 0 ) {
@@ -1388,10 +1608,14 @@ setTransformation( WrapOperation, MoveOperation, ( a, b ) => {
 	} );
 } );
 
-setTransformation( WrapOperation, SplitOperation, ( a, b ) => {
+setTransformation( WrapOperation, SplitOperation, ( a, b, context ) => {
 	// Case 1:	If range to wrap got split by split operation cancel the wrapping.
+	//			Do that only if this is not undo mode. If `b` operation was earlier transformed by unwrap operation
+	//			and the split position was inside the unwrapped range, then proceed without special case.
 	//
-	if ( a.position.hasSameParentAs( b.position ) && a.wrappedRange.containsPosition( b.position ) ) {
+	const isInside = a.position.hasSameParentAs( b.position ) && a.wrappedRange.containsPosition( b.position );
+
+	if ( isInside && context.getRelation( b, a ) !== 'splitInside' ) {
 		// We cannot just return no-op in this case, because in the mirror case scenario the wrap is reversed, which
 		// might introduce a new node in the graveyard (if the wrap didn't have `graveyardPosition`, then the wrap
 		// created a new element which was put to the graveyard when the wrap was reversed).
@@ -1401,7 +1625,7 @@ setTransformation( WrapOperation, SplitOperation, ( a, b ) => {
 			const graveyard = a.position.root.document.graveyard;
 			const graveyardPosition = new Position( graveyard, [ 0 ] );
 
-			return new InsertOperation( graveyardPosition, a.element, 0 );
+			return [ new InsertOperation( graveyardPosition, a.element, 0 ) ];
 		} else {
 			return getNoOp();
 		}
@@ -1622,7 +1846,7 @@ setTransformation( UnwrapOperation, MergeOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( UnwrapOperation, MoveOperation, ( a, b, context ) => {
+setTransformation( UnwrapOperation, MoveOperation, ( a, b ) => {
 	// Case 1:	Move operation moves nodes from the unwrapped element.
 	//			This does not have any impact on `UnwrapOperation#position`, but `#howMany` has to be changed.
 	//
@@ -1640,7 +1864,7 @@ setTransformation( UnwrapOperation, MoveOperation, ( a, b, context ) => {
 
 	a.position = a.position._getTransformedByMoveOperation( b );
 
-	if ( !a.graveyardPosition.isEqual( b.targetPosition ) || !context.aIsStrong ) {
+	if ( !a.graveyardPosition.isEqual( b.targetPosition ) ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
@@ -1691,6 +1915,10 @@ setTransformation( UnwrapOperation, WrapOperation, ( a, b ) => {
 		a.howMany = a.howMany - b.howMany + 1;
 	}
 
+	if ( b.graveyardPosition && compareArrays( a.position.getParentPath(), b.graveyardPosition.path ) == 'same' ) {
+		a.howMany = b.howMany;
+	}
+
 	// The default case.
 	//
 	a.position = a.position._getTransformedByWrapOperation( b );
@@ -1709,6 +1937,8 @@ setTransformation( UnwrapOperation, UnwrapOperation, ( a, b, context ) => {
 		a.position = new Position( b.graveyardPosition.root, path );
 		a.howMany = 0;
 		a.graveyardPosition = Position.createFromPosition( b.graveyardPosition );
+
+		return [ a ];
 	}
 
 	a.position = a.position._getTransformedByUnwrapOperation( b );
@@ -1759,8 +1989,7 @@ function makeMoveOperationsFromRanges( ranges, targetPosition ) {
 			ranges[ j ] = ranges[ j ]._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany )[ 0 ];
 		}
 
-		// targetPosition.stickiness = 'toPrevious';
-		targetPosition = targetPosition._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany, true );
+		targetPosition = targetPosition._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany );
 	}
 
 	return operations;
diff --git a/src/model/position.js b/src/model/position.js
index ced1b8abc..21ec4d4b9 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -761,6 +761,7 @@ export default class Position {
 
 		// The first part of a path to combined position is a path to the place where nodes were moved.
 		const combined = Position.createFromPosition( target );
+		combined.stickiness = this.stickiness;
 
 		// Then we have to update the rest of the path.
 
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index fc1f222f6..d90a85111 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -53,6 +53,12 @@ describe( 'transform', () => {
 		}
 	}
 
+	const contextIsStrong = {
+		aIsStrong: true,
+		wasUndone: () => false,
+		getRelation: () => false
+	};
+
 	describe( 'InsertOperation', () => {
 		let nodeC, nodeD, position;
 
@@ -119,7 +125,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -310,7 +316,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -862,7 +868,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.oldValue = 'xyz';
 
@@ -1102,7 +1108,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1241,7 +1247,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1567,7 +1573,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.sourcePosition.path = [ 4, 1, 0 ];
 
@@ -1599,7 +1605,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.sourcePosition.path = [ 4, 1, 1 ];
 
@@ -1637,7 +1643,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1675,7 +1681,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1714,7 +1720,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1765,7 +1771,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1805,7 +1811,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1830,7 +1836,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1901,7 +1907,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 3 );
 
@@ -1952,7 +1958,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1975,7 +1981,7 @@ describe( 'transform', () => {
 			} );
 
 			it( 'should skip context.aIsStrong and be less important than RemoveOperation', () => {
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2318,7 +2324,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2611,7 +2617,7 @@ describe( 'transform', () => {
 				const anotherRange = Range.createFromParentsAndOffsets( root, 2, root, 2 );
 				const transformBy = new MarkerOperation( 'name', oldRange, anotherRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.oldRange = anotherRange;
 
diff --git a/tests/model/operation/transform/attribute.js b/tests/model/operation/transform/attribute.js
index 6a5d0f775..3e8610442 100644
--- a/tests/model/operation/transform/attribute.js
+++ b/tests/model/operation/transform/attribute.js
@@ -795,7 +795,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>FooB<$text bold="true">ar</$text></paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #2, then undo', () => {
+			it( 'element into paragraph #2, then undo', () => {
 				john.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
diff --git a/tests/model/operation/transform/insert.js b/tests/model/operation/transform/insert.js
index 635116e14..3eb36286b 100644
--- a/tests/model/operation/transform/insert.js
+++ b/tests/model/operation/transform/insert.js
@@ -811,7 +811,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>Foo</paragraph><paragraph>BarAbc</paragraph>' );
 			} );
 
-			it.skip( 'element, then add marker, split and undo with type #2', () => {
+			it( 'element, then add marker, split and undo with type #2', () => {
 				john.setData( '<paragraph>Foo</paragraph>[]' );
 				kate.setData( '[<paragraph>Foo</paragraph>]' );
 
@@ -845,8 +845,6 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual content:
-				// <paragraph></paragraph><paragraph>Ba</paragraph><paragraph></paragraph>
 				expectClients( '<paragraph>Foo</paragraph><paragraph>BarAbc</paragraph>' );
 			} );
 		} );
diff --git a/tests/model/operation/transform/marker.js b/tests/model/operation/transform/marker.js
index 07b4a2f2b..bb3cf0902 100644
--- a/tests/model/operation/transform/marker.js
+++ b/tests/model/operation/transform/marker.js
@@ -183,7 +183,6 @@ describe( 'transform', () => {
 				kate.remove();
 
 				syncClients();
-
 				expectClients( '<paragraph></paragraph>' );
 
 				john.undo();
@@ -191,8 +190,7 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual result for Kate:
-				// <paragraph><m1:start></m1:start>Fo<m1:end></m1:end><m2:start></m2:start>o<m2:end></m2:end> Bar</paragraph>
+				// Wrong markers transforming.
 				expectClients(
 					'<paragraph>' +
 						'<m1:start></m1:start>Foo<m1:end></m1:end><m2:start></m2:start> Bar<m2:end></m2:end>' +
diff --git a/tests/model/operation/transform/move.js b/tests/model/operation/transform/move.js
index f54108ef8..a7868903b 100644
--- a/tests/model/operation/transform/move.js
+++ b/tests/model/operation/transform/move.js
@@ -335,7 +335,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'text in other user\'s selection', () => {
+			it( 'text in other user\'s selection', () => {
 				john.setData( '<paragraph>[Foo] Bar</paragraph>' );
 				kate.setData( '<paragraph>F[]oo Bar</paragraph>' );
 
@@ -366,7 +366,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'inside moved text', () => {
+			it( 'inside moved text', () => {
 				john.setData( '<paragraph>F[oo Ba]r</paragraph><paragraph>Abc</paragraph>' );
 				kate.setData( '<paragraph>Foo[] Bar</paragraph><paragraph>Abc</paragraph>' );
 
@@ -375,10 +375,6 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual result for Kate:
-				// <paragraph>F</paragraph><paragraph>r</paragraph><paragraph> BaooAbc</paragraph>
-				// Move operations have wrong targets when they target at same place.
-
 				expectClients(
 					'<paragraph>F</paragraph>' +
 					'<paragraph>r</paragraph>' +
diff --git a/tests/model/operation/transform/remove.js b/tests/model/operation/transform/remove.js
index 92cbc090b..8e2fdcf18 100644
--- a/tests/model/operation/transform/remove.js
+++ b/tests/model/operation/transform/remove.js
@@ -218,7 +218,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element while removing, then undo', () => {
+			it( 'element while removing, then undo', () => {
 				john.setData( '<paragraph>Foo</paragraph><blockQuote>[<paragraph>Bar</paragraph>]</blockQuote>' );
 				kate.setData( '<paragraph>Foo</paragraph><blockQuote>[]<paragraph>Bar</paragraph></blockQuote>' );
 
@@ -226,15 +226,11 @@ describe( 'transform', () => {
 				kate.unwrap();
 
 				syncClients();
-
 				expectClients( '<paragraph>Foo</paragraph>' );
 
 				john.undo();
 
 				syncClients();
-
-				// Actual result:
-				// <paragraph>Foo</paragraph><blockQuote></blockQuote>
 				expectClients(
 					'<paragraph>Foo</paragraph>' +
 					'<paragraph>Bar</paragraph>'
@@ -443,7 +439,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element into paragraph, then undo', () => {
+			it( 'element into paragraph, then undo', () => {
 				john.setData( '<paragraph>F[oo]</paragraph><paragraph>Bar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -451,15 +447,11 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
-
 				expectClients( '<paragraph>FBar</paragraph>' );
 
 				john.undo();
 
 				syncClients();
-
-				// Actual result:
-				// <paragraph>F<paragraph></paragraph>oBar</paragraph>
 				expectClients( '<paragraph>FooBar</paragraph>' );
 			} );
 
diff --git a/tests/model/operation/transform/split.js b/tests/model/operation/transform/split.js
index 7f02b915c..e1b46a707 100644
--- a/tests/model/operation/transform/split.js
+++ b/tests/model/operation/transform/split.js
@@ -90,7 +90,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap', () => {
+			it( 'intersecting wrap', () => {
 				john.setData( '<paragraph>Fo[]o</paragraph>' );
 				kate.setData( '<paragraph>F[oo]</paragraph>' );
 
@@ -98,10 +98,9 @@ describe( 'transform', () => {
 				kate.wrap( 'div' );
 
 				syncClients();
-
 				expectClients(
-					'<paragraph>F</paragraph>' +
-					'<paragraph><div>oo</div></paragraph>'
+					'<paragraph>Fo</paragraph>' +
+					'<paragraph>o</paragraph>'
 				);
 			} );
 		} );
@@ -122,7 +121,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element in same position', () => {
+			it( 'element in same position', () => {
 				john.setData( '<blockQuote><paragraph>[]Foo</paragraph></blockQuote>' );
 				kate.setData( '<blockQuote><paragraph>[]Foo</paragraph></blockQuote>' );
 
@@ -130,7 +129,6 @@ describe( 'transform', () => {
 				kate.unwrap();
 
 				syncClients();
-
 				expectClients( '<blockQuote>Foo</blockQuote>' );
 			} );
 
@@ -285,7 +283,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>FooBar</paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #3', () => {
+			it( 'element into paragraph #3', () => {
 				john.setData( '<paragraph>Foo[]</paragraph><paragraph>Bar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -299,13 +297,10 @@ describe( 'transform', () => {
 				kate.undo();
 
 				syncClients();
-				// Actual content for Kate:
-				// <paragraph>FooBar</paragraph><paragraph></paragraph>
-				// There is a problem in Merge x Split transform in undo case.
 				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #4', () => {
+			it( 'element into paragraph #4', () => {
 				john.setData( '<paragraph>Foo</paragraph><paragraph>B[]ar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -313,14 +308,16 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
+				expectClients(
+					'<paragraph>FooB</paragraph>' +
+					'<paragraph>ar</paragraph>'
+				);
 
 				john.undo();
 				kate.undo();
 
-				expectClients(
-					'<paragraph>Fo</paragraph>' +
-					'<paragraph>oBar</paragraph>'
-				);
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 		} );
 
diff --git a/tests/model/operation/transform/unwrap.js b/tests/model/operation/transform/unwrap.js
index 0b14ddd1b..8cba9be85 100644
--- a/tests/model/operation/transform/unwrap.js
+++ b/tests/model/operation/transform/unwrap.js
@@ -50,7 +50,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>Foo</paragraph>' );
 			} );
 
-			it.skip( 'the same element, then undo', () => {
+			it( 'the same element, then undo', () => {
 				john.setData( '<blockQuote>[]<paragraph>Foo</paragraph></blockQuote>' );
 				kate.setData( '<blockQuote>[]<paragraph>Foo</paragraph></blockQuote>' );
 
@@ -63,9 +63,6 @@ describe( 'transform', () => {
 				john.undo();
 
 				syncClients();
-				// Actual content for Kate:
-				// <paragraph><paragraph>Foo</paragraph></paragraph>
-				// Kate has a different order of nodes in graveyard after syncing.
 				expectClients( '<blockQuote><paragraph>Foo</paragraph></blockQuote>' );
 			} );
 		} );
diff --git a/tests/model/operation/transform/utils.js b/tests/model/operation/transform/utils.js
index 8a0557151..016842f9c 100644
--- a/tests/model/operation/transform/utils.js
+++ b/tests/model/operation/transform/utils.js
@@ -253,16 +253,34 @@ function bufferOperations( operations, client ) {
 }
 
 export function syncClients() {
-	for ( const client of clients ) {
-		for ( const item of bufferedOperations ) {
-			const remoteOperations = item.operations.map( op => OperationFactory.fromJSON( JSON.parse( op ), client.document ) );
-			const remoteClient = item.client;
+	const clientsOperations = {};
+
+	// For each client, flatten all buffered operations into one set.
+	for ( const item of bufferedOperations ) {
+		const name = item.client.name;
+
+		if ( !clientsOperations[ name ] ) {
+			clientsOperations[ name ] = [];
+		}
+
+		clientsOperations[ name ].push( ...item.operations );
+	}
 
-			if ( remoteClient == client ) {
+	for ( const localClient of clients ) {
+		for ( const remoteClient of clients ) {
+			if ( remoteClient == localClient ) {
 				continue;
 			}
 
-			const clientOperations = Array.from( client.document.history.getOperations( client.syncedVersion ) );
+			const remoteOperationsJson = clientsOperations[ remoteClient.name ];
+
+			if ( !remoteOperationsJson ) {
+				continue;
+			}
+
+			const remoteOperations = remoteOperationsJson.map( op => OperationFactory.fromJSON( JSON.parse( op ), localClient.document ) );
+
+			const localOperations = Array.from( localClient.document.history.getOperations( localClient.syncedVersion ) );
 
 			let remoteOperationsTransformed = null;
 
@@ -271,21 +289,21 @@ export function syncClients() {
 				padWithNoOps: true
 			};
 
-			if ( client.orderNumber < remoteClient.orderNumber ) {
-				remoteOperationsTransformed = transform.transformSets( clientOperations, remoteOperations, options ).operationsB;
+			if ( localClient.orderNumber < remoteClient.orderNumber ) {
+				remoteOperationsTransformed = transform.transformSets( localOperations, remoteOperations, options ).operationsB;
 			} else {
-				remoteOperationsTransformed = transform.transformSets( remoteOperations, clientOperations, options ).operationsA;
+				remoteOperationsTransformed = transform.transformSets( remoteOperations, localOperations, options ).operationsA;
 			}
 
-			client.editor.model.enqueueChange( 'transparent', writer => {
+			localClient.editor.model.enqueueChange( 'transparent', writer => {
 				for ( const operation of remoteOperationsTransformed ) {
 					writer.batch.addOperation( operation );
-					client.editor.model.applyOperation( operation );
+					localClient.editor.model.applyOperation( operation );
 				}
 			} );
 		}
 
-		client.syncedVersion = client.document.version;
+		localClient.syncedVersion = localClient.document.version;
 	}
 
 	bufferedOperations.clear();
diff --git a/tests/model/operation/transform/wrap.js b/tests/model/operation/transform/wrap.js
index f7e125980..a24e011be 100644
--- a/tests/model/operation/transform/wrap.js
+++ b/tests/model/operation/transform/wrap.js
@@ -63,19 +63,24 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap #2', () => {
-				john.setData( '<paragraph>[Foo]</paragraph>' );
-				kate.setData( '<paragraph>F[o]o</paragraph>' );
+			it( 'intersecting wrap #2', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
+				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
 
-				john.wrap( 'div' );
+				john.wrap( 'blockQuote' );
 				kate.wrap( 'div' );
 
 				syncClients();
-
-				expectClients( '<paragraph><div>Foo</div></pragraph>' );
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+						'<paragraph>Abc</paragraph>' +
+					'</blockQuote>'
+				);
 			} );
 
-			it.skip( 'intersecting wrap, then undo #1', () => {
+			it( 'intersecting wrap, then undo #1', () => {
 				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
 
@@ -83,12 +88,20 @@ describe( 'transform', () => {
 				kate.wrap( 'div' );
 
 				syncClients();
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+					'</blockQuote>' +
+					'<div>' +
+						'<paragraph>Abc</paragraph>' +
+					'</div>'
+				);
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
-
 				expectClients(
 					'<paragraph>Foo</paragraph>' +
 					'<paragraph>Bar</paragraph>' +
@@ -96,21 +109,30 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap, then undo #2', () => {
-				john.setData( '<paragraph>[Foo]</paragraph>' );
-				kate.setData( '<paragraph>F[o]o</paragraph>' );
+			it( 'intersecting wrap, then undo #2', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
+				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
 
-				john.wrap( 'div' );
+				john.wrap( 'blockQuote' );
 				kate.wrap( 'div' );
 
 				syncClients();
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+					'</blockQuote>' +
+					'<div>' +
+						'<paragraph>Abc</paragraph>' +
+					'</div>'
+				);
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
 
-				expectClients( '<paragraph><div>Foo</div></pragraph>' );
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph><paragraph>Abc</paragraph>' );
 			} );
 
 			it( 'element and text', () => {
@@ -227,14 +249,12 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
-
-				expectClients( '<blockQuote><paragraph>FooBar</paragraph></blockQuote>' );
+				expectClients( '<paragraph>FooBar</paragraph><blockQuote></blockQuote>' );
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
-
 				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 		} );

From 3f1cd6e3096a82707846eb9e20d69efdf736b59e Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 13:14:07 +0200
Subject: [PATCH 02/26] Docs: Fixed docs errors.

---
 src/model/operation/operation.js | 12 ++----------
 src/model/position.js            |  2 +-
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/src/model/operation/operation.js b/src/model/operation/operation.js
index 965f365bc..9ad9e58fc 100644
--- a/src/model/operation/operation.js
+++ b/src/model/operation/operation.js
@@ -49,14 +49,6 @@ export default class Operation {
 		 * @member {String} #type
 		 */
 
-		/**
-		 * {@link module:engine/model/operation/operation~Operation Operation} which the operation is a part of. This property is set by the
-		 * {@link module:engine/model/operation/operation~Operation operation} when the operations is added to it by the
-		 * {@link module:engine/model/operation/operation~Operation#addOperation} method.
-		 *
-		 * @member {module:engine/model/operation/operation~Operation} #operation
-		 */
-
 		/**
 		 * Creates and returns an operation that has the same parameters as this operation.
 		 *
@@ -70,8 +62,8 @@ export default class Operation {
 		 * operation execution. In other words, it reverses changes done by the original operation.
 		 *
 		 * Keep in mind that tree model state may change since executing the original operation,
-		 * so reverse operation will be "outdated". In that case you will need to
-		 * {@link module:engine/model/operation/transform~transform} it by all operations that were executed after the original operation.
+		 * so reverse operation will be "outdated". In that case you will need to transform it by
+		 * all operations that were executed after the original operation.
 		 *
 		 * @method #getReversed
 		 * @returns {module:engine/model/operation/operation~Operation} Reversed operation.
diff --git a/src/model/position.js b/src/model/position.js
index 21ec4d4b9..4a91b11f9 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -22,7 +22,7 @@ import Text from './text';
  *
  * Since position in a model is represented by a {@link module:engine/model/position~Position#root position root} and
  * {@link module:engine/model/position~Position#path position path} it is possible to create positions placed in non-existing elements.
- * This requirement is important for {@link module:engine/model/operation/transform~transform operational transformation}.
+ * This requirement is important for operational transformation.
  *
  * Also, {@link module:engine/model/operation/operation~Operation operations}
  * kept in {@link module:engine/model/document~Document#history document history}

From b00e548bb3f99212fe8caff4e8934a69c2bb8444 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 14:26:10 +0200
Subject: [PATCH 03/26] Fix: Use numbers instead of booleans in Array.sort.

---
 src/dev-utils/model.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/dev-utils/model.js b/src/dev-utils/model.js
index 7f1aa5713..8b1529624 100644
--- a/src/dev-utils/model.js
+++ b/src/dev-utils/model.js
@@ -249,7 +249,7 @@ export function stringify( node, selectionOrPositionOrRange = null, markers = nu
 
 	if ( markers ) {
 		// To provide stable results, sort markers by name.
-		markers = Array.from( markers ).sort( ( a, b ) => a.name < b.name );
+		markers = Array.from( markers ).sort( ( a, b ) => a.name < b.name ? 1 : -1 );
 
 		for ( const marker of markers ) {
 			downcastDispatcher.convertMarkerAdd( marker.name, marker.getRange(), writer );

From 828cc082fd7eda76f6f23c15f818eddf2b692b13 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 15:44:18 +0200
Subject: [PATCH 04/26] Changed: Moved transformation error logging from debug
 tools to OT code.

---
 src/dev-utils/enableenginedebug.js   | 19 ----------------
 src/model/operation/transform.js     | 17 +++++++++++++-
 tests/dev-utils/enableenginedebug.js | 34 ----------------------------
 tests/model/operation/transform.js   | 23 +++++++++++++++++++
 4 files changed, 39 insertions(+), 54 deletions(-)

diff --git a/src/dev-utils/enableenginedebug.js b/src/dev-utils/enableenginedebug.js
index a1f990100..45dda9372 100644
--- a/src/dev-utils/enableenginedebug.js
+++ b/src/dev-utils/enableenginedebug.js
@@ -25,7 +25,6 @@ import MoveOperation from '../model/operation/moveoperation';
 import NoOperation from '../model/operation/nooperation';
 import RenameOperation from '../model/operation/renameoperation';
 import RootAttributeOperation from '../model/operation/rootattributeoperation';
-import transform from '../model/operation/transform';
 import Model from '../model/model';
 import ModelDocument from '../model/document';
 import ModelDocumentFragment from '../model/documentfragment';
@@ -349,24 +348,6 @@ function enableLoggingTools() {
 			`"${ this.key }": ${ JSON.stringify( this.oldValue ) } -> ${ JSON.stringify( this.newValue ) }, ${ this.root.rootName }`;
 	} );
 
-	const _transformTransform = transform.transform;
-
-	sandbox.mock( transform, 'transform', function( a, b, context ) {
-		let results;
-
-		try {
-			results = _transformTransform( a, b, context );
-		} catch ( e ) {
-			logger.error( 'Error during operation transformation!' );
-			logger.error( a.toString() + ( context.isStrong ? ' (important)' : '' ) );
-			logger.error( b.toString() + ( context.isStrong ? '' : ' (important)' ) );
-
-			throw e;
-		}
-
-		return results;
-	} );
-
 	sandbox.mock( ViewText.prototype, 'toString', function() {
 		return `#${ this.data }`;
 	} );
diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index ee05eee28..1a0322d86 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -13,7 +13,9 @@ import UnwrapOperation from './unwrapoperation';
 import NoOperation from './nooperation';
 import Range from '../range';
 import Position from '../position';
+
 import compareArrays from '@ckeditor/ckeditor5-utils/src/comparearrays';
+import log from '@ckeditor/ckeditor5-utils/src/log';
 
 const transformations = new Map();
 
@@ -75,7 +77,20 @@ function updateBaseVersions( operations, baseVersion ) {
 function transform( a, b, context = { aIsStrong: false, wasUndone: () => false, getRelation: () => null } ) {
 	const transformationFunction = getTransformation( a, b );
 
-	return transformationFunction( a.clone(), b, context );
+	try {
+		return transformationFunction( a.clone(), b, context );
+	} catch ( e ) {
+		log.error( 'Error during operation transformation!' );
+		log.error( 'Transformed operation', a );
+		log.error( 'Operation transformed by', b );
+		log.error( 'context.aIsStrong', context.aIsStrong );
+		log.error( 'context.wasUndone( a )', context.wasUndone( a ) );
+		log.error( 'context.wasUndone( b )', context.wasUndone( b ) );
+		log.error( 'context.getRelation( a, b )', context.getRelation( a, b ) );
+		log.error( 'context.getRelation( b, a )', context.getRelation( b, a ) );
+
+		throw e;
+	}
 }
 
 function transformSets( operationsA, operationsB, options ) {
diff --git a/tests/dev-utils/enableenginedebug.js b/tests/dev-utils/enableenginedebug.js
index 4b586ac48..ffbdf8b7e 100644
--- a/tests/dev-utils/enableenginedebug.js
+++ b/tests/dev-utils/enableenginedebug.js
@@ -22,7 +22,6 @@ import NoOperation from '../../src/model/operation/nooperation';
 import RenameOperation from '../../src/model/operation/renameoperation';
 import RootAttributeOperation from '../../src/model/operation/rootattributeoperation';
 import RemoveOperation from '../../src/model/operation/removeoperation';
-import transform from '../../src/model/operation/transform';
 import Model from '../../src/model/model';
 import ModelDocumentFragment from '../../src/model/documentfragment';
 
@@ -668,39 +667,6 @@ describe( 'debug tools', () => {
 		} );
 	} );
 
-	describe( 'should provide error logging for transformation', () => {
-		let model, document, root, otherRoot;
-
-		beforeEach( () => {
-			model = new Model();
-			document = model.document;
-			root = document.createRoot();
-			otherRoot = document.createRoot( 'other', 'other' );
-		} );
-
-		it.skip( 'with more important operation A', () => {
-			const opA = new MoveOperation( ModelPosition.createAt( root, 4 ), 4, ModelPosition.createAt( otherRoot, 4 ), 0 );
-			const opB = new InsertOperation( ModelPosition.createAt( root, 0 ), new ModelText( 'a' ), 0 );
-
-			expect( () => {
-				transform.transform( opA, opB, { isStrong: true } );
-			} ).to.throw( Error );
-			expect( error.calledWith( opA.toString() + ' (important)' ) ).to.be.true;
-			expect( error.calledWith( opB.toString() ) ).to.be.true;
-		} );
-
-		it.skip( 'with more important operation B', () => {
-			const opA = new MoveOperation( ModelPosition.createAt( root, 4 ), 4, ModelPosition.createAt( otherRoot, 4 ), 0 );
-			const opB = new InsertOperation( ModelPosition.createAt( root, 0 ), new ModelText( 'a' ), 0 );
-
-			testUtils.sinon.stub( transform, 'transform' ).throws( new Error() );
-
-			expect( () => transform.transform( opA, opB, { isStrong: true } ) ).to.throw( Error );
-			expect( error.calledWith( opA.toString() ) ).to.be.true;
-			expect( error.calledWith( opB.toString() + ' (important)' ) ).to.be.true;
-		} );
-	} );
-
 	function expectLog( expectedLogMsg ) {
 		expect( log.calledWithExactly( expectedLogMsg ) ).to.be.true;
 		log.resetHistory();
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index d90a85111..2ef0c60a8 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -20,6 +20,8 @@ import RemoveOperation from '../../../src/model/operation/removeoperation';
 import RenameOperation from '../../../src/model/operation/renameoperation';
 import NoOperation from '../../../src/model/operation/nooperation';
 
+import log from '@ckeditor/ckeditor5-utils/src/log';
+
 describe( 'transform', () => {
 	let model, doc, root, op, nodeA, nodeB, expected;
 
@@ -59,6 +61,27 @@ describe( 'transform', () => {
 		getRelation: () => false
 	};
 
+	it( 'error logging', () => {
+		const spy = sinon.spy( log, 'error' );
+
+		const nodeA = new Node();
+		const nodeB = new Node();
+
+		const position = new Position( root, [ 0 ] );
+
+		const a = new InsertOperation( position, [ nodeA ], 0 );
+		const b = new InsertOperation( position, [ nodeB ], 0 );
+
+		// Modify an operation so it will throw an error.
+		a.position = null;
+
+		expect( () => {
+			transform.transform( a, b );
+		} ).to.throw();
+
+		sinon.assert.called( spy );
+	} );
+
 	describe( 'InsertOperation', () => {
 		let nodeC, nodeD, position;
 

From db1299dca4beb7df06dc32fd3beb171b645e2224 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 16:37:50 +0200
Subject: [PATCH 05/26] Docs: Improved error docs.

---
 src/model/selection.js           | 16 +++++++++++++++-
 src/view/selection.js            | 10 +++++++++-
 tests/model/documentselection.js |  2 +-
 tests/model/selection.js         |  2 +-
 tests/view/documentselection.js  |  4 ++--
 tests/view/selection.js          |  4 ++--
 6 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/src/model/selection.js b/src/model/selection.js
index 4a2bf2c29..8e1c989ac 100644
--- a/src/model/selection.js
+++ b/src/model/selection.js
@@ -431,7 +431,21 @@ export default class Selection {
 		// Check whether there is any range in new ranges set that is different than all already added ranges.
 		const anyNewRange = newRanges.some( newRange => {
 			if ( !( newRange instanceof Range ) ) {
-				throw new CKEditorError( 'model-selection-added-not-range: Trying to add an object that is not an instance of Range.' );
+				/**
+				 * Selection range set to an object that is not an instance of {@link module:engine/model/range~Range}.
+				 *
+				 * Only {@link module:engine/model/range~Range} instances can be used to set a selection.
+				 * Common mistakes leading to this error are:
+				 *
+				 * * using DOM `Range` object,
+				 * * incorrect CKEditor 5 installation with multiple `ckeditor5-engine` packages having different versions.
+				 *
+				 * @error model-selection-set-ranges-not-range
+				 */
+				throw new CKEditorError(
+					'model-selection-set-ranges-not-range: ' +
+					'Selection range set to an object that is not an instance of model.Range.'
+				);
 			}
 
 			return this._ranges.every( oldRange => {
diff --git a/src/view/selection.js b/src/view/selection.js
index bd132dac8..e8b00e75a 100644
--- a/src/view/selection.js
+++ b/src/view/selection.js
@@ -643,7 +643,15 @@ export default class Selection {
 	 */
 	_addRange( range, isBackward = false ) {
 		if ( !( range instanceof Range ) ) {
-			throw new CKEditorError( 'view-selection-invalid-range: Invalid Range.' );
+			/**
+			 * Selection range set to an object that is not an instance of {@link module:engine/view/range~Range}.
+			 *
+			 * @error view-selection-add-range-not-range
+			 */
+			throw new CKEditorError(
+				'view-selection-add-range-not-range: ' +
+				'Selection range set to an object that is not an instance of view.Range'
+			);
 		}
 
 		this._pushRange( range );
diff --git a/tests/model/documentselection.js b/tests/model/documentselection.js
index 8a5a89852..299b06913 100644
--- a/tests/model/documentselection.js
+++ b/tests/model/documentselection.js
@@ -334,7 +334,7 @@ describe( 'DocumentSelection', () => {
 		it( 'should throw an error when range is invalid', () => {
 			expect( () => {
 				selection._setTo( [ { invalid: 'range' } ] );
-			} ).to.throw( CKEditorError, /model-selection-added-not-range/ );
+			} ).to.throw( CKEditorError, /model-selection-set-ranges-not-range/ );
 		} );
 
 		it( 'should log a warning when trying to set selection to the graveyard', () => {
diff --git a/tests/model/selection.js b/tests/model/selection.js
index 4439e9012..630420c5c 100644
--- a/tests/model/selection.js
+++ b/tests/model/selection.js
@@ -633,7 +633,7 @@ describe( 'Selection', () => {
 		it( 'should throw an error when range is invalid', () => {
 			expect( () => {
 				selection._setRanges( [ { invalid: 'range' } ] );
-			} ).to.throw( CKEditorError, /model-selection-added-not-range/ );
+			} ).to.throw( CKEditorError, /model-selection-set-ranges-not-range/ );
 		} );
 
 		it( 'should remove all ranges and add given ranges', () => {
diff --git a/tests/view/documentselection.js b/tests/view/documentselection.js
index 4525b544e..78ca8a11d 100644
--- a/tests/view/documentselection.js
+++ b/tests/view/documentselection.js
@@ -113,7 +113,7 @@ describe( 'DocumentSelection', () => {
 			expect( () => {
 				// eslint-disable-next-line no-new
 				new DocumentSelection( [ { invalid: 'range' } ] );
-			} ).to.throw( CKEditorError, 'view-selection-invalid-range: Invalid Range.' );
+			} ).to.throw( CKEditorError, /view-selection-add-range-not-range/ );
 		} );
 
 		it( 'should throw an error when ranges intersects', () => {
@@ -1004,7 +1004,7 @@ describe( 'DocumentSelection', () => {
 			it( 'should throw an error when range is invalid', () => {
 				expect( () => {
 					documentSelection._setTo( [ { invalid: 'range' } ] );
-				} ).to.throw( CKEditorError, 'view-selection-invalid-range: Invalid Range.' );
+				} ).to.throw( CKEditorError, /view-selection-add-range-not-range/ );
 			} );
 
 			it( 'should throw when range is intersecting with already added range', () => {
diff --git a/tests/view/selection.js b/tests/view/selection.js
index 910f20123..6c503e9d1 100644
--- a/tests/view/selection.js
+++ b/tests/view/selection.js
@@ -113,7 +113,7 @@ describe( 'Selection', () => {
 			expect( () => {
 				// eslint-disable-next-line no-new
 				new Selection( [ { invalid: 'range' } ] );
-			} ).to.throw( CKEditorError, 'view-selection-invalid-range: Invalid Range.' );
+			} ).to.throw( CKEditorError, /view-selection-add-range-not-range/ );
 		} );
 
 		it( 'should throw an error when ranges intersects', () => {
@@ -878,7 +878,7 @@ describe( 'Selection', () => {
 			it( 'should throw an error when range is invalid', () => {
 				expect( () => {
 					selection.setTo( [ { invalid: 'range' } ] );
-				} ).to.throw( CKEditorError, 'view-selection-invalid-range: Invalid Range.' );
+				} ).to.throw( CKEditorError, /view-selection-add-range-not-range/ );
 			} );
 
 			it( 'should throw when range is intersecting with already added range', () => {

From 63adf00e85dc4c432c426dc5ed33d175a9f6ce3e Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 16:54:04 +0200
Subject: [PATCH 06/26] Changed: Improved WrapOperation implementation.

---
 src/model/operation/wrapoperation.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/model/operation/wrapoperation.js b/src/model/operation/wrapoperation.js
index 5de2c6a68..7b7cf533b 100644
--- a/src/model/operation/wrapoperation.js
+++ b/src/model/operation/wrapoperation.js
@@ -148,7 +148,10 @@ export default class WrapOperation extends Operation {
 		const targetPosition = new Position( this.position.root, targetPath );
 
 		if ( this.element ) {
-			_insert( insertPosition, this.element._clone() );
+			const originalElement = this.element;
+			this.element = this.element._clone();
+
+			_insert( insertPosition, originalElement );
 		} else {
 			_move( Range.createFromPositionAndShift( this.graveyardPosition, 1 ), insertPosition );
 		}

From aae2bea5b7737a15e65acf42a3ed9f703d3de47f Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 12:33:05 +0200
Subject: [PATCH 07/26] Changed: Schema#getValidRanges now returns flat ranges,
 compatible with the new AttributeOperation.

---
 src/model/schema.js   |  76 ++++++++++++++-----
 tests/model/schema.js | 172 +++++++++++++++++++++++++-----------------
 2 files changed, 161 insertions(+), 87 deletions(-)

diff --git a/src/model/schema.js b/src/model/schema.js
index 61cca5ff2..da6a66aa3 100644
--- a/src/model/schema.js
+++ b/src/model/schema.js
@@ -668,35 +668,60 @@ export default class Schema {
 	 * @returns {Array.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
 	 */
 	getValidRanges( ranges, attribute ) {
-		const validRanges = [];
+		ranges = convertToMinimalFlatRanges( ranges );
+		const result = [];
 
 		for ( const range of ranges ) {
-			let last = range.start;
-			let from = range.start;
-			const to = range.end;
-
-			for ( const value of range.getWalker() ) {
-				if ( !this.checkAttribute( value.item, attribute ) ) {
-					if ( !from.isEqual( last ) ) {
-						validRanges.push( new Range( from, last ) );
-					}
+			const validRanges = this._getValidRangesForRange( range, attribute );
 
-					from = value.nextPosition;
-				}
+			result.push( ...validRanges );
+		}
+
+		return result;
+	}
+
+	/**
+	 * Takes a flat range and an attribute name. Traverses the range recursively and deeply to find and return all ranges
+	 * inside the given range on which the attribute can be applied.
+	 *
+	 * This is a helper function for {@link ~Schema#getValidRanges}.
+	 *
+	 * @private
+	 * @param {module:engine/model/range~Range} range Range to process.
+	 * @param {String} attribute The name of the attribute to check.
+	 * @returns {Array.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
+	 */
+	_getValidRangesForRange( range, attribute ) {
+		const result = [];
 
-				last = value.nextPosition;
+		let start = range.start;
+		let end = range.start;
+
+		for ( const item of range.getItems( { shallow: true } ) ) {
+			if ( item.is( 'element' ) ) {
+				result.push( ...this._getValidRangesForRange( Range.createIn( item ), attribute ) );
 			}
 
-			if ( from && !from.isEqual( to ) ) {
-				validRanges.push( new Range( from, to ) );
+			if ( !this.checkAttribute( item, attribute ) ) {
+				if ( !start.isEqual( end ) ) {
+					result.push( new Range( start, end ) );
+				}
+
+				start = Position.createAfter( item );
 			}
+
+			end = Position.createAfter( item );
 		}
 
-		return validRanges;
+		if ( !start.isEqual( end ) ) {
+			result.push( new Range( start, end ) );
+		}
+
+		return result;
 	}
 
 	/**
-	 * Basing on given the `position`, finds and returns a {@link module:engine/model/range~Range range} which is
+	 * Basing on given `position`, finds and returns a {@link module:engine/model/range~Range range} which is
 	 * nearest to that `position` and is a correct range for selection.
 	 *
 	 * The correct selection range might be collapsed when it is located in a position where the text node can be placed.
@@ -1572,3 +1597,20 @@ function* combineWalkers( backward, forward ) {
 		}
 	}
 }
+
+// Takes an array of non-intersecting ranges. For each of them gets minimal flat ranges covering that range and returns
+// all those minimal flat ranges.
+//
+// @param {Array.<module:engine/model/range~Range>} ranges Ranges to process.
+// @returns {Array.<module:engine/model/range~Range>} Minimal flat ranges of given `ranges`.
+function convertToMinimalFlatRanges( ranges ) {
+	const result = [];
+
+	for ( const range of ranges ) {
+		const minimal = range.getMinimalFlatRanges();
+
+		result.push( ...minimal );
+	}
+
+	return result;
+}
diff --git a/tests/model/schema.js b/tests/model/schema.js
index 55c01041b..fd85549a7 100644
--- a/tests/model/schema.js
+++ b/tests/model/schema.js
@@ -1106,8 +1106,7 @@ describe( 'Schema', () => {
 	} );
 
 	describe( 'getValidRanges()', () => {
-		const attribute = 'bold';
-		let model, doc, root, schema, ranges;
+		let model, doc, root, schema;
 
 		beforeEach( () => {
 			model = new Model();
@@ -1116,112 +1115,145 @@ describe( 'Schema', () => {
 			root = doc.createRoot();
 
 			schema.register( 'p', { inheritAllFrom: '$block' } );
-			schema.register( 'h1', { inheritAllFrom: '$block' } );
-			schema.register( 'img', {
-				allowWhere: '$text'
-			} );
+			schema.register( 'img', { allowWhere: '$text' } );
 
-			schema.addAttributeCheck( ( ctx, attributeName ) => {
-				// Allow 'bold' on p>$text.
-				if ( ctx.endsWith( 'p $text' ) && attributeName == 'bold' ) {
-					return true;
-				}
+			// This is a "hack" to allow setting any ranges in `setData` util.
+			schema.extend( '$text', { allowIn: '$root' } );
+		} );
 
-				// Allow 'bold' on $root>p.
-				if ( ctx.endsWith( '$root p' ) && attributeName == 'bold' ) {
-					return true;
-				}
-			} );
+		function test( input, attribute, output ) {
+			setData( model, input );
 
-			// Parse data string to model.
-			const parsedModel = parse( '<p>foo<img />bar</p>', model.schema, { context: [ root.name ] } );
+			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
+			const sel = new Selection( validRanges );
 
-			// Set parsed model data to prevent selection post-fixer from running.
-			model.change( writer => {
-				writer.insert( parsedModel, root );
-			} );
+			expect( stringify( root, sel ) ).to.equal( output );
+		}
 
-			ranges = [ Range.createOn( root.getChild( 0 ) ) ];
+		it( 'should return a range with p for an attribute allowed only on p', () => {
+			schema.extend( 'p', { allowAttributes: 'foo' } );
+
+			test(
+				'[<p>foo<img></img>bar</p>]',
+				'foo',
+				'[<p>foo<img></img>bar</p>]'
+			);
 		} );
 
-		it( 'should return unmodified ranges when attribute is allowed on each item (text is not allowed in img)', () => {
-			schema.extend( 'img', { allowAttributes: 'bold' } );
+		it( 'should return ranges on text nodes for an attribute allowed only on text', () => {
+			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			expect( schema.getValidRanges( ranges, attribute ) ).to.deep.equal( ranges );
+			test(
+				'[<p>foo<img></img>bar</p>]',
+				'bold',
+				'<p>[foo]<img></img>[bar]</p>'
+			);
 		} );
 
-		it( 'should return unmodified ranges when attribute is allowed on each item (text is allowed in img)', () => {
-			schema.extend( 'img', { allowAttributes: 'bold' } );
-			schema.extend( '$text', { allowIn: 'img' } );
+		it( 'should return a range on img for an attribute allowed only on img', () => {
+			schema.extend( 'img', { allowAttributes: 'src' } );
 
-			expect( schema.getValidRanges( ranges, attribute ) ).to.deep.equal( ranges );
+			test(
+				'[<p>foo<img></img>bar</p>]',
+				'src',
+				'<p>foo[<img></img>]bar</p>'
+			);
 		} );
 
-		it( 'should return two ranges when attribute is not allowed on one item', () => {
+		it( 'should return a range containing all children for an attribute allowed on all children', () => {
+			schema.extend( '$text', { allowAttributes: 'bold' } );
 			schema.extend( 'img', { allowAttributes: 'bold' } );
-			schema.extend( '$text', { allowIn: 'img' } );
 
-			setData( model, '<p>[foo<img>xxx</img>bar]</p>' );
+			test(
+				'[<p>foo<img></img>bar</p>]',
+				'bold',
+				'<p>[foo<img></img>bar]</p>'
+			);
+		} );
 
-			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
-			const sel = new Selection( validRanges );
+		it( 'should return a range with p and a range on all children for an attribute allowed on p and its children', () => {
+			schema.extend( 'p', { allowAttributes: 'foo' } );
+			schema.extend( '$text', { allowAttributes: 'foo' } );
+			schema.extend( 'img', { allowAttributes: 'foo' } );
 
-			expect( stringify( root, sel ) ).to.equal( '<p>[foo<img>]xxx[</img>bar]</p>' );
-		} );
+			setData( model, '[<p>foo<img></img>bar</p>]' );
 
-		it( 'should return three ranges when attribute is not allowed on one element but is allowed on its child', () => {
-			schema.extend( '$text', { allowIn: 'img' } );
+			const validRanges = schema.getValidRanges( doc.selection.getRanges(), 'foo' );
 
-			schema.addAttributeCheck( ( ctx, attributeName ) => {
-				// Allow 'bold' on img>$text.
-				if ( ctx.endsWith( 'img $text' ) && attributeName == 'bold' ) {
-					return true;
-				}
-			} );
+			expect( validRanges.length ).to.equal( 2 );
 
-			setData( model, '<p>[foo<img>xxx</img>bar]</p>' );
+			expect( validRanges[ 0 ].start.path ).to.deep.equal( [ 0, 0 ] );
+			expect( validRanges[ 0 ].end.path ).to.deep.equal( [ 0, 7 ] );
 
-			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
-			const sel = new Selection( validRanges );
+			expect( validRanges[ 1 ].start.path ).to.deep.equal( [ 0 ] );
+			expect( validRanges[ 1 ].end.path ).to.deep.equal( [ 1 ] );
+		} );
+
+		it( 'should not break a range if children are not allowed to have the attribute', () => {
+			schema.extend( 'p', { allowAttributes: 'foo' } );
 
-			expect( stringify( root, sel ) ).to.equal( '<p>[foo]<img>[xxx]</img>[bar]</p>' );
+			test(
+				'[<p>foo</p><p>bar</p>]',
+				'foo',
+				'[<p>foo</p><p>bar</p>]'
+			);
 		} );
 
-		it( 'should not leak beyond the given ranges', () => {
-			setData( model, '<p>[foo<img></img>bar]x[bar<img></img>foo]</p>' );
+		it( 'should search deeply', () => {
+			schema.extend( '$text', { allowAttributes: 'bold', allowIn: 'img' } );
 
-			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
-			const sel = new Selection( validRanges );
+			test(
+				'[<p>foo<img>xxx</img>bar</p>]',
+				'bold',
+				'<p>[foo]<img>[xxx]</img>[bar]</p>'
+			);
+		} );
+
+		it( 'should work with multiple ranges', () => {
+			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			expect( stringify( root, sel ) ).to.equal( '<p>[foo]<img></img>[bar]x[bar]<img></img>[foo]</p>' );
+			test(
+				'[<p>a</p><p>b</p>]<p>c</p><p>[d]</p>',
+				'bold',
+				'<p>[a]</p><p>[b]</p><p>c</p><p>[d]</p>'
+			);
 		} );
 
-		it( 'should correctly handle a range which ends in a disallowed position', () => {
-			schema.extend( '$text', { allowIn: 'img' } );
+		it( 'should work with non-flat ranges', () => {
+			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			setData( model, '<p>[foo<img>bar]</img>bom</p>' );
+			test(
+				'[<p>a</p><p>b</p><p>c]</p><p>d</p>',
+				'bold',
+				'<p>[a]</p><p>[b]</p><p>[c]</p><p>d</p>'
+			);
+		} );
 
-			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
-			const sel = new Selection( validRanges );
+		it( 'should not leak beyond the given ranges', () => {
+			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			expect( stringify( root, sel ) ).to.equal( '<p>[foo]<img>bar</img>bom</p>' );
+			test(
+				'[<p>foo</p><p>b]a[r</p><p>x]yz</p>',
+				'bold',
+				'<p>[foo]</p><p>[b]a[r]</p><p>[x]yz</p>'
+			);
 		} );
 
-		it( 'should split range into two ranges and omit disallowed element', () => {
+		it( 'should correctly handle a range which ends in a disallowed position', () => {
+			schema.extend( '$text', { allowAttributes: 'bold', allowIn: 'img' } );
+
+			// Disallow bold on text inside image.
 			schema.addAttributeCheck( ( ctx, attributeName ) => {
-				// Disallow 'bold' on p>img.
-				if ( ctx.endsWith( 'p img' ) && attributeName == 'bold' ) {
+				if ( ctx.endsWith( 'img $text' ) && attributeName == 'bold' ) {
 					return false;
 				}
 			} );
 
-			const result = schema.getValidRanges( ranges, attribute );
-
-			expect( result ).to.length( 2 );
-			expect( result[ 0 ].start.path ).to.members( [ 0 ] );
-			expect( result[ 0 ].end.path ).to.members( [ 0, 3 ] );
-			expect( result[ 1 ].start.path ).to.members( [ 0, 4 ] );
-			expect( result[ 1 ].end.path ).to.members( [ 1 ] );
+			test(
+				'[<p>foo<img>xx]x</img>bar</p>',
+				'bold',
+				'<p>[foo]<img>xxx</img>bar</p>'
+			);
 		} );
 	} );
 

From 7b6057bddb1461c5e0adf161dfd2ff93e3fe72ff Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 13:22:15 +0200
Subject: [PATCH 08/26] Changed: Remove `ReinsertOperation` and
 `RemoveOperation`.

---
 src/model/operation/detachoperation.js     |   1 -
 src/model/operation/insertoperation.js     |   6 +-
 src/model/operation/moveoperation.js       |   6 +
 src/model/operation/operationfactory.js    |   4 -
 src/model/operation/reinsertoperation.js   |  76 --------
 src/model/operation/removeoperation.js     |  60 -------
 src/model/operation/transform.js           |  55 +-----
 src/model/writer.js                        |   5 +-
 tests/dev-utils/enableenginedebug.js       |   5 +-
 tests/model/differ.js                      |   3 +-
 tests/model/documentselection.js           |  11 +-
 tests/model/operation/insertoperation.js   |   6 +-
 tests/model/operation/moveoperation.js     |  20 ++-
 tests/model/operation/reinsertoperation.js | 157 -----------------
 tests/model/operation/removeoperation.js   | 191 ---------------------
 tests/model/operation/transform.js         |  19 +-
 tests/model/range.js                       |   9 +-
 tests/model/writer.js                      |   2 +-
 18 files changed, 57 insertions(+), 579 deletions(-)
 delete mode 100644 src/model/operation/reinsertoperation.js
 delete mode 100644 src/model/operation/removeoperation.js
 delete mode 100644 tests/model/operation/reinsertoperation.js
 delete mode 100644 tests/model/operation/removeoperation.js

diff --git a/src/model/operation/detachoperation.js b/src/model/operation/detachoperation.js
index 5441991fa..6da08e0d2 100644
--- a/src/model/operation/detachoperation.js
+++ b/src/model/operation/detachoperation.js
@@ -60,7 +60,6 @@ export default class DetachOperation extends Operation {
 		if ( this.sourcePosition.root.document ) {
 			/**
 			 * Cannot detach document node.
-			 * Use {@link module:engine/model/operation/removeoperation~RemoveOperation remove operation} instead.
 			 *
 			 * @error detach-operation-on-document-node
 			 */
diff --git a/src/model/operation/insertoperation.js b/src/model/operation/insertoperation.js
index a67577758..f5aa6a9dc 100644
--- a/src/model/operation/insertoperation.js
+++ b/src/model/operation/insertoperation.js
@@ -10,7 +10,7 @@
 import Operation from './operation';
 import Position from '../position';
 import NodeList from '../nodelist';
-import RemoveOperation from './removeoperation';
+import MoveOperation from './moveoperation';
 import { _insert, _normalizeNodes } from './utils';
 import Text from '../text';
 import Element from '../element';
@@ -87,13 +87,13 @@ export default class InsertOperation extends Operation {
 	/**
 	 * See {@link module:engine/model/operation/operation~Operation#getReversed `Operation#getReversed()`}.
 	 *
-	 * @returns {module:engine/model/operation/removeoperation~RemoveOperation}
+	 * @returns {module:engine/model/operation/moveoperation~MoveOperation}
 	 */
 	getReversed() {
 		const graveyard = this.position.root.document.graveyard;
 		const gyPosition = new Position( graveyard, [ 0 ] );
 
-		return new RemoveOperation( this.position, this.nodes.maxOffset, gyPosition, this.baseVersion + 1 );
+		return new MoveOperation( this.position, this.nodes.maxOffset, gyPosition, this.baseVersion + 1 );
 	}
 
 	/**
diff --git a/src/model/operation/moveoperation.js b/src/model/operation/moveoperation.js
index 3672cee28..6ba3e841c 100644
--- a/src/model/operation/moveoperation.js
+++ b/src/model/operation/moveoperation.js
@@ -64,6 +64,12 @@ export default class MoveOperation extends Operation {
 	 * @inheritDoc
 	 */
 	get type() {
+		if ( this.targetPosition.root.rootName == '$graveyard' ) {
+			return 'remove';
+		} else if ( this.sourcePosition.root.rootName == '$graveyard' ) {
+			return 'reinsert';
+		}
+
 		return 'move';
 	}
 
diff --git a/src/model/operation/operationfactory.js b/src/model/operation/operationfactory.js
index d30dbc7ae..b5c02c4e3 100644
--- a/src/model/operation/operationfactory.js
+++ b/src/model/operation/operationfactory.js
@@ -13,8 +13,6 @@ import MarkerOperation from '../operation/markeroperation';
 import MoveOperation from '../operation/moveoperation';
 import NoOperation from '../operation/nooperation';
 import Operation from '../operation/operation';
-import ReinsertOperation from '../operation/reinsertoperation';
-import RemoveOperation from '../operation/removeoperation';
 import RenameOperation from '../operation/renameoperation';
 import RootAttributeOperation from '../operation/rootattributeoperation';
 import SplitOperation from '../operation/splitoperation';
@@ -29,8 +27,6 @@ operations[ MarkerOperation.className ] = MarkerOperation;
 operations[ MoveOperation.className ] = MoveOperation;
 operations[ NoOperation.className ] = NoOperation;
 operations[ Operation.className ] = Operation;
-operations[ ReinsertOperation.className ] = ReinsertOperation;
-operations[ RemoveOperation.className ] = RemoveOperation;
 operations[ RenameOperation.className ] = RenameOperation;
 operations[ RootAttributeOperation.className ] = RootAttributeOperation;
 operations[ SplitOperation.className ] = SplitOperation;
diff --git a/src/model/operation/reinsertoperation.js b/src/model/operation/reinsertoperation.js
deleted file mode 100644
index 270884e7f..000000000
--- a/src/model/operation/reinsertoperation.js
+++ /dev/null
@@ -1,76 +0,0 @@
-/**
- * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
- * For licensing, see LICENSE.md.
- */
-
-/**
- * @module engine/model/operation/reinsertoperation
- */
-
-import MoveOperation from './moveoperation';
-import RemoveOperation from './removeoperation';
-import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
-
-/**
- * Operation to reinsert previously removed nodes back to the non-graveyard root. This operation acts like
- * {@link module:engine/model/operation/moveoperation~MoveOperation} but it returns
- * {@link module:engine/model/operation/removeoperation~RemoveOperation} when reversed
- * and fires different change event.
- */
-export default class ReinsertOperation extends MoveOperation {
-	/**
-	 * Position where nodes will be re-inserted.
-	 *
-	 * @type {module:engine/model/position~Position}
-	 */
-	get position() {
-		return this.targetPosition;
-	}
-
-	/**
-	 * @param {module:engine/model/position~Position} pos
-	 */
-	set position( pos ) {
-		this.targetPosition = pos;
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	get type() {
-		return 'reinsert';
-	}
-
-	/**
-	 * See {@link module:engine/model/operation/operation~Operation#getReversed `Operation#getReversed()`}.
-	 *
-	 * @returns {module:engine/model/operation/removeoperation~RemoveOperation}
-	 */
-	getReversed() {
-		const newTargetPosition = this.sourcePosition._getTransformedByInsertion( this.targetPosition, this.howMany );
-
-		return new RemoveOperation( this.getMovedRangeStart(), this.howMany, newTargetPosition, this.baseVersion + 1 );
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	_validate() {
-		super._validate();
-
-		if ( !this.sourcePosition.root.document ) {
-			throw new CKEditorError( 'reinsert-operation-on-detached-item: Cannot reinsert detached item.' );
-		}
-
-		if ( !this.targetPosition.root.document ) {
-			throw new CKEditorError( 'reinsert-operation-to-detached-parent: Cannot reinsert item to detached parent.' );
-		}
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	static get className() {
-		return 'engine.model.operation.ReinsertOperation';
-	}
-}
diff --git a/src/model/operation/removeoperation.js b/src/model/operation/removeoperation.js
deleted file mode 100644
index ba26e3629..000000000
--- a/src/model/operation/removeoperation.js
+++ /dev/null
@@ -1,60 +0,0 @@
-/**
- * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
- * For licensing, see LICENSE.md.
- */
-
-/**
- * @module engine/model/operation/removeoperation
- */
-
-import MoveOperation from './moveoperation';
-import ReinsertOperation from './reinsertoperation';
-import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
-
-/**
- * Operation to remove a range of nodes.
- */
-export default class RemoveOperation extends MoveOperation {
-	/**
-	 * @inheritDoc
-	 */
-	get type() {
-		return 'remove';
-	}
-
-	/**
-	 * See {@link module:engine/model/operation/operation~Operation#getReversed `Operation#getReversed()`}.
-	 *
-	 * @returns {module:engine/model/operation/reinsertoperation~ReinsertOperation|module:engine/model/operation/nooperation~NoOperation}
-	 */
-	getReversed() {
-		const newTargetPosition = this.sourcePosition._getTransformedByInsertion( this.targetPosition, this.howMany );
-
-		return new ReinsertOperation( this.getMovedRangeStart(), this.howMany, newTargetPosition, this.baseVersion + 1 );
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	_validate() {
-		super._validate();
-
-		if ( !this.sourcePosition.root.document ) {
-			/**
-			 * Item that is going to be removed needs to be a {@link module:engine/model/document~Document document} child.
-			 * To remove Item from detached document fragment use
-			 * {@link module:engine/model/operation/detachoperation~DetachOperation DetachOperation}.
-			 *
-			 * @error remove-operation-on-detached-item
-			 */
-			throw new CKEditorError( 'remove-operation-on-detached-item: Cannot remove detached item.' );
-		}
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	static get className() {
-		return 'engine.model.operation.RemoveOperation';
-	}
-}
diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index f0a9dba73..4517ccee2 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -3,8 +3,6 @@ import AttributeOperation from './attributeoperation';
 import RenameOperation from './renameoperation';
 import MarkerOperation from './markeroperation';
 import MoveOperation from './moveoperation';
-import RemoveOperation from './removeoperation';
-import ReinsertOperation from './reinsertoperation';
 import RootAttributeOperation from './rootattributeoperation';
 import MergeOperation from './mergeoperation';
 import SplitOperation from './splitoperation';
@@ -29,32 +27,10 @@ function setTransformation( OperationA, OperationB, transformationFunction ) {
 }
 
 function getTransformation( a, b ) {
-	const OperationA = a.constructor;
-	const OperationB = b.constructor;
+	const aGroup = transformations.get( a.constructor );
 
-	const aGroups = new Set();
-	const aGroup = transformations.get( OperationA );
-
-	if ( aGroup ) {
-		aGroups.add( aGroup );
-	}
-
-	for ( const Operation of transformations.keys() ) {
-		if ( a instanceof Operation ) {
-			aGroups.add( transformations.get( Operation ) );
-		}
-	}
-
-	for ( const group of aGroups ) {
-		if ( group.has( OperationB ) ) {
-			return group.get( OperationB );
-		}
-
-		for ( const Operation of group.keys() ) {
-			if ( b instanceof Operation ) {
-				return group.get( Operation );
-			}
-		}
+	if ( aGroup && aGroup.has( b.constructor ) ) {
+		return aGroup.get( b.constructor );
 	}
 
 	return noUpdateTransformation;
@@ -707,7 +683,7 @@ setTransformation( MergeOperation, MoveOperation, ( a, b, context ) => {
 	//
 	const removedRange = Range.createFromPositionAndShift( b.sourcePosition, b.howMany );
 
-	if ( b instanceof RemoveOperation && !context.wasUndone( b ) ) {
+	if ( b.type == 'remove' && !context.wasUndone( b ) ) {
 		if ( a.deletionPosition.hasSameParentAs( b.sourcePosition ) && removedRange.containsPosition( a.sourcePosition ) ) {
 			return getNoOp();
 		}
@@ -926,9 +902,9 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 	//
 	// If only one of operations is a remove operation, we force remove operation to be the "stronger" one
 	// to provide more expected results.
-	if ( a instanceof RemoveOperation && !( b instanceof RemoveOperation ) ) {
+	if ( a.type == 'remove' && b.type != 'remove' ) {
 		aIsStrong = true;
-	} else if ( !( a instanceof RemoveOperation ) && b instanceof RemoveOperation ) {
+	} else if ( a.type != 'remove' && b.type == 'remove' ) {
 		aIsStrong = false;
 	}
 
@@ -1050,7 +1026,7 @@ setTransformation( MoveOperation, MergeOperation, ( a, b, context ) => {
 	const movedRange = Range.createFromPositionAndShift( a.sourcePosition, a.howMany );
 
 	if ( b.deletionPosition.hasSameParentAs( a.sourcePosition ) && movedRange.containsPosition( b.sourcePosition ) ) {
-		if ( a instanceof RemoveOperation ) {
+		if ( a.type == 'remove' ) {
 			// Case 1:	The element to remove got merged.
 			//			Merge operation does support merging elements which are not siblings. So it would not be a problem
 			//			from technical point of view. However, if the element was removed, the intention of the user
@@ -1767,25 +1743,12 @@ function makeMoveOperationsFromRanges( ranges, targetPosition ) {
 }
 
 function makeMoveOperation( range, targetPosition ) {
-	// We want to keep correct operation class.
-	let OperationClass;
-
-	if ( targetPosition.root.rootName == '$graveyard' ) {
-		OperationClass = RemoveOperation;
-	} else if ( range.start.root.rootName == '$graveyard' ) {
-		OperationClass = ReinsertOperation;
-	} else {
-		OperationClass = MoveOperation;
-	}
-
 	targetPosition.stickiness = 'toNone';
 
-	const result = new OperationClass(
+	return new MoveOperation(
 		range.start,
 		range.end.offset - range.start.offset,
 		targetPosition,
-		0 // Is corrected anyway later.
+		0
 	);
-
-	return result;
 }
diff --git a/src/model/writer.js b/src/model/writer.js
index 41000fa43..8b6e00043 100644
--- a/src/model/writer.js
+++ b/src/model/writer.js
@@ -12,7 +12,6 @@ import DetachOperation from './operation/detachoperation';
 import InsertOperation from './operation/insertoperation';
 import MarkerOperation from './operation/markeroperation';
 import MoveOperation from './operation/moveoperation';
-import RemoveOperation from './operation/removeoperation';
 import RenameOperation from './operation/renameoperation';
 import RootAttributeOperation from './operation/rootattributeoperation';
 import SplitOperation from './operation/splitoperation';
@@ -1330,7 +1329,7 @@ function applyMarkerOperation( writer, name, oldRange, newRange, affectsData ) {
 	model.applyOperation( operation );
 }
 
-// Creates `RemoveOperation` or `DetachOperation` that removes `howMany` nodes starting from `position`.
+// Creates `MoveOperation` or `DetachOperation` that removes `howMany` nodes starting from `position`.
 // The operation will be applied on given model instance and added to given operation instance.
 //
 // @private
@@ -1345,7 +1344,7 @@ function applyRemoveOperation( position, howMany, batch, model ) {
 		const doc = model.document;
 		const graveyardPosition = new Position( doc.graveyard, [ 0 ] );
 
-		operation = new RemoveOperation( position, howMany, graveyardPosition, doc.version );
+		operation = new MoveOperation( position, howMany, graveyardPosition, doc.version );
 	} else {
 		operation = new DetachOperation( position, howMany );
 	}
diff --git a/tests/dev-utils/enableenginedebug.js b/tests/dev-utils/enableenginedebug.js
index 4b586ac48..c3eec4f3c 100644
--- a/tests/dev-utils/enableenginedebug.js
+++ b/tests/dev-utils/enableenginedebug.js
@@ -21,7 +21,6 @@ import MoveOperation from '../../src/model/operation/moveoperation';
 import NoOperation from '../../src/model/operation/nooperation';
 import RenameOperation from '../../src/model/operation/renameoperation';
 import RootAttributeOperation from '../../src/model/operation/rootattributeoperation';
-import RemoveOperation from '../../src/model/operation/removeoperation';
 import transform from '../../src/model/operation/transform';
 import Model from '../../src/model/model';
 import ModelDocumentFragment from '../../src/model/documentfragment';
@@ -532,8 +531,8 @@ describe( 'debug tools', () => {
 				model.applyOperation( insert );
 
 				const graveyard = modelDoc.graveyard;
-				const remove = new RemoveOperation( ModelPosition.createAt( modelRoot, 1 ), 2, ModelPosition.createAt( graveyard, 0 ), 1 );
-				model.applyOperation( remove );
+				const move = new MoveOperation( ModelPosition.createAt( modelRoot, 1 ), 2, ModelPosition.createAt( graveyard, 0 ), 1 );
+				model.applyOperation( move );
 			} );
 
 			log.resetHistory();
diff --git a/tests/model/differ.js b/tests/model/differ.js
index d04e3b54c..549146cae 100644
--- a/tests/model/differ.js
+++ b/tests/model/differ.js
@@ -10,7 +10,6 @@ import Position from '../../src/model/position';
 import Range from '../../src/model/range';
 
 import InsertOperation from '../../src/model/operation/insertoperation';
-import RemoveOperation from '../../src/model/operation/removeoperation';
 import MoveOperation from '../../src/model/operation/moveoperation';
 import RenameOperation from '../../src/model/operation/renameoperation';
 import AttributeOperation from '../../src/model/operation/attributeoperation';
@@ -1617,7 +1616,7 @@ describe( 'Differ', () => {
 
 	function remove( sourcePosition, howMany ) {
 		const targetPosition = Position.createAt( doc.graveyard, doc.graveyard.maxOffset );
-		const operation = new RemoveOperation( sourcePosition, howMany, targetPosition, doc.version );
+		const operation = new MoveOperation( sourcePosition, howMany, targetPosition, doc.version );
 
 		model.applyOperation( operation );
 	}
diff --git a/tests/model/documentselection.js b/tests/model/documentselection.js
index 8a5a89852..1f12e172d 100644
--- a/tests/model/documentselection.js
+++ b/tests/model/documentselection.js
@@ -13,7 +13,6 @@ import LiveRange from '../../src/model/liverange';
 import DocumentSelection from '../../src/model/documentselection';
 import InsertOperation from '../../src/model/operation/insertoperation';
 import MoveOperation from '../../src/model/operation/moveoperation';
-import RemoveOperation from '../../src/model/operation/removeoperation';
 import AttributeOperation from '../../src/model/operation/attributeoperation';
 import SplitOperation from '../../src/model/operation/splitoperation';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
@@ -1131,12 +1130,12 @@ describe( 'DocumentSelection', () => {
 			} );
 		} );
 
-		describe( 'RemoveOperation', () => {
+		describe( 'MoveOperation to graveyard', () => {
 			it( 'fix selection range if it ends up in graveyard #1', () => {
 				selection._setTo( new Position( root, [ 1, 3 ] ) );
 
 				model.applyOperation(
-					new RemoveOperation(
+					new MoveOperation(
 						new Position( root, [ 1, 2 ] ),
 						2,
 						new Position( doc.graveyard, [ 0 ] ),
@@ -1151,7 +1150,7 @@ describe( 'DocumentSelection', () => {
 				selection._setTo( [ new Range( new Position( root, [ 1, 2 ] ), new Position( root, [ 1, 4 ] ) ) ] );
 
 				model.applyOperation(
-					new RemoveOperation(
+					new MoveOperation(
 						new Position( root, [ 1, 2 ] ),
 						2,
 						new Position( doc.graveyard, [ 0 ] ),
@@ -1166,7 +1165,7 @@ describe( 'DocumentSelection', () => {
 				selection._setTo( [ new Range( new Position( root, [ 1, 1 ] ), new Position( root, [ 1, 2 ] ) ) ] );
 
 				model.applyOperation(
-					new RemoveOperation(
+					new MoveOperation(
 						new Position( root, [ 1 ] ),
 						2,
 						new Position( doc.graveyard, [ 0 ] ),
@@ -1179,7 +1178,7 @@ describe( 'DocumentSelection', () => {
 
 			it( 'fix selection range if it ends up in graveyard #4 - whole content removed', () => {
 				model.applyOperation(
-					new RemoveOperation(
+					new MoveOperation(
 						new Position( root, [ 0 ] ),
 						3,
 						new Position( doc.graveyard, [ 0 ] ),
diff --git a/tests/model/operation/insertoperation.js b/tests/model/operation/insertoperation.js
index 6f59cf3dc..92d7749a1 100644
--- a/tests/model/operation/insertoperation.js
+++ b/tests/model/operation/insertoperation.js
@@ -7,7 +7,7 @@ import Model from '../../../src/model/model';
 import NodeList from '../../../src/model/nodelist';
 import Element from '../../../src/model/element';
 import InsertOperation from '../../../src/model/operation/insertoperation';
-import RemoveOperation from '../../../src/model/operation/removeoperation';
+import MoveOperation from '../../../src/model/operation/moveoperation';
 import Position from '../../../src/model/position';
 import Text from '../../../src/model/text';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
@@ -107,7 +107,7 @@ describe( 'InsertOperation', () => {
 		expect( root.getChild( 0 ).data ).to.equal( 'fooxbar' );
 	} );
 
-	it( 'should create a RemoveOperation as a reverse', () => {
+	it( 'should create a MoveOperation as a reverse', () => {
 		const position = new Position( root, [ 0 ] );
 		const operation = new InsertOperation(
 			position,
@@ -117,7 +117,7 @@ describe( 'InsertOperation', () => {
 
 		const reverse = operation.getReversed();
 
-		expect( reverse ).to.be.an.instanceof( RemoveOperation );
+		expect( reverse ).to.be.an.instanceof( MoveOperation );
 		expect( reverse.baseVersion ).to.equal( 1 );
 		expect( reverse.sourcePosition.isEqual( position ) ).to.be.true;
 		expect( reverse.howMany ).to.equal( 7 );
diff --git a/tests/model/operation/moveoperation.js b/tests/model/operation/moveoperation.js
index d2ff1edde..6e3a86a00 100644
--- a/tests/model/operation/moveoperation.js
+++ b/tests/model/operation/moveoperation.js
@@ -12,23 +12,27 @@ import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
 import { jsonParseStringify } from '../../../tests/model/_utils/utils';
 
 describe( 'MoveOperation', () => {
-	let model, doc, root;
+	let model, doc, root, gy;
 
 	beforeEach( () => {
 		model = new Model();
 		doc = model.document;
 		root = doc.createRoot();
+		gy = doc.graveyard;
 	} );
 
 	it( 'should have proper type', () => {
-		const op = new MoveOperation(
-			new Position( root, [ 0, 0 ] ),
-			1,
-			new Position( root, [ 1, 0 ] ),
-			doc.version
-		);
+		const move = new MoveOperation( new Position( root, [ 0, 0 ] ), 1, new Position( root, [ 1, 0 ] ), 0 );
+		expect( move.type ).to.equal( 'move' );
+
+		const remove1 = new MoveOperation( new Position( root, [ 0, 0 ] ), 1, new Position( gy, [ 0 ] ), 0 );
+		expect( remove1.type ).to.equal( 'remove' );
+
+		const remove2 = new MoveOperation( new Position( gy, [ 0 ] ), 1, new Position( gy, [ 1 ] ), 0 );
+		expect( remove2.type ).to.equal( 'remove' );
 
-		expect( op.type ).to.equal( 'move' );
+		const reinsert = new MoveOperation( new Position( gy, [ 0 ] ), 1, new Position( root, [ 0, 0 ] ), 0 );
+		expect( reinsert.type ).to.equal( 'reinsert' );
 	} );
 
 	it( 'should move from one node to another', () => {
diff --git a/tests/model/operation/reinsertoperation.js b/tests/model/operation/reinsertoperation.js
deleted file mode 100644
index da927dfc2..000000000
--- a/tests/model/operation/reinsertoperation.js
+++ /dev/null
@@ -1,157 +0,0 @@
-/**
- * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
- * For licensing, see LICENSE.md.
- */
-
-import Model from '../../../src/model/model';
-import ReinsertOperation from '../../../src/model/operation/reinsertoperation';
-import RemoveOperation from '../../../src/model/operation/removeoperation';
-import MoveOperation from '../../../src/model/operation/moveoperation';
-import Position from '../../../src/model/position';
-import DocumentFragment from '../../../src/model/documentfragment';
-import Element from '../../../src/model/element';
-import Text from '../../../src/model/text';
-import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
-import { jsonParseStringify } from '../../../tests/model/_utils/utils';
-
-describe( 'ReinsertOperation', () => {
-	let model, doc, root, graveyard, operation, graveyardPosition, rootPosition;
-
-	beforeEach( () => {
-		model = new Model();
-		doc = model.document;
-		root = doc.createRoot();
-		graveyard = doc.graveyard;
-
-		graveyardPosition = new Position( graveyard, [ 0 ] );
-		rootPosition = new Position( root, [ 0 ] );
-
-		operation = new ReinsertOperation(
-			graveyardPosition,
-			2,
-			rootPosition,
-			doc.version
-		);
-	} );
-
-	it( 'should have position property equal to the position where node will be reinserted', () => {
-		expect( operation.position.isEqual( rootPosition ) ).to.be.true;
-
-		// Setting also works:
-		operation.position = new Position( root, [ 1 ] );
-		expect( operation.position.isEqual( new Position( root, [ 1 ] ) ) ).to.be.true;
-	} );
-
-	it( 'should have proper type', () => {
-		expect( operation.type ).to.equal( 'reinsert' );
-	} );
-
-	it( 'should extend MoveOperation class', () => {
-		expect( operation ).to.be.instanceof( MoveOperation );
-	} );
-
-	it( 'should create ReinsertOperation with same parameters when cloned', () => {
-		const clone = operation.clone();
-
-		expect( clone ).to.be.instanceof( ReinsertOperation );
-		expect( clone.sourcePosition.isEqual( operation.sourcePosition ) ).to.be.true;
-		expect( clone.targetPosition.isEqual( operation.targetPosition ) ).to.be.true;
-		expect( clone.howMany ).to.equal( operation.howMany );
-		expect( clone.baseVersion ).to.equal( operation.baseVersion );
-	} );
-
-	it( 'should create RemoveOperation as a reverse', () => {
-		graveyard._appendChild( new Element( 'x' ) );
-
-		const reverse = operation.getReversed();
-
-		expect( reverse ).to.be.an.instanceof( RemoveOperation );
-		expect( reverse.baseVersion ).to.equal( 1 );
-		expect( reverse.howMany ).to.equal( 2 );
-		expect( reverse.sourcePosition.isEqual( rootPosition ) ).to.be.true;
-		expect( reverse.targetPosition.isEqual( graveyardPosition ) ).to.be.true;
-	} );
-
-	it( 'should create correct RemoveOperation when reversed if target position was in graveyard', () => {
-		const operation = new ReinsertOperation( new Position( doc.graveyard, [ 0 ] ), 1, new Position( doc.graveyard, [ 3 ] ), 0 );
-		const reverse = operation.getReversed();
-
-		expect( reverse.sourcePosition.path ).to.deep.equal( [ 2 ] );
-		expect( reverse.targetPosition.path ).to.deep.equal( [ 0 ] );
-	} );
-
-	it( 'should undo reinsert set of nodes by applying reverse operation', () => {
-		const reverse = operation.getReversed();
-
-		graveyard._insertChild( 0, new Text( 'xx' ) );
-
-		model.applyOperation( operation );
-
-		expect( doc.version ).to.equal( 1 );
-		expect( root.maxOffset ).to.equal( 2 );
-		expect( graveyard.maxOffset ).to.equal( 0 );
-
-		model.applyOperation( reverse );
-
-		expect( doc.version ).to.equal( 2 );
-		expect( root.maxOffset ).to.equal( 0 );
-		expect( graveyard.maxOffset ).to.equal( 2 );
-	} );
-
-	describe( '_validate()', () => {
-		it( 'should throw when target position is not in the document', () => {
-			const docFrag = new DocumentFragment();
-
-			graveyard._insertChild( 0, new Text( 'xx' ) );
-
-			operation = new ReinsertOperation(
-				graveyardPosition,
-				1,
-				Position.createAt( docFrag ),
-				doc.version
-			);
-
-			expect( () => {
-				operation._validate();
-			} ).to.throw( CKEditorError, /^reinsert-operation-to-detached-parent/ );
-		} );
-
-		it( 'should throw when source position is not in the document', () => {
-			const docFrag = new DocumentFragment( new Text( 'xx' ) );
-
-			operation = new ReinsertOperation(
-				Position.createAt( docFrag ),
-				1,
-				rootPosition,
-				doc.version
-			);
-
-			expect( () => {
-				operation._validate();
-			} ).to.throw( CKEditorError, /^reinsert-operation-on-detached-item/ );
-		} );
-	} );
-
-	describe( 'toJSON', () => {
-		it( 'should create proper json object', () => {
-			const serialized = jsonParseStringify( operation );
-
-			expect( serialized ).to.deep.equal( {
-				__className: 'engine.model.operation.ReinsertOperation',
-				baseVersion: 0,
-				howMany: 2,
-				sourcePosition: jsonParseStringify( operation.sourcePosition ),
-				targetPosition: jsonParseStringify( operation.targetPosition )
-			} );
-		} );
-	} );
-
-	describe( 'fromJSON', () => {
-		it( 'should create proper ReinsertOperation from json object', () => {
-			const serialized = jsonParseStringify( operation );
-			const deserialized = ReinsertOperation.fromJSON( serialized, doc );
-
-			expect( deserialized ).to.deep.equal( operation );
-		} );
-	} );
-} );
diff --git a/tests/model/operation/removeoperation.js b/tests/model/operation/removeoperation.js
deleted file mode 100644
index da9bf72b1..000000000
--- a/tests/model/operation/removeoperation.js
+++ /dev/null
@@ -1,191 +0,0 @@
-/**
- * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
- * For licensing, see LICENSE.md.
- */
-
-import Model from '../../../src/model/model';
-import ReinsertOperation from '../../../src/model/operation/reinsertoperation';
-import RemoveOperation from '../../../src/model/operation/removeoperation';
-import MoveOperation from '../../../src/model/operation/moveoperation';
-import Position from '../../../src/model/position';
-import DocumentFragment from '../../../src/model/documentfragment';
-import Element from '../../../src/model/element';
-import Text from '../../../src/model/text';
-import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
-import { jsonParseStringify } from '../../../tests/model/_utils/utils';
-
-describe( 'RemoveOperation', () => {
-	let model, doc, root, graveyard;
-
-	beforeEach( () => {
-		model = new Model();
-		doc = model.document;
-		root = doc.createRoot();
-		graveyard = doc.graveyard;
-	} );
-
-	it( 'should have proper type', () => {
-		const op = new RemoveOperation(
-			new Position( root, [ 2 ] ),
-			2,
-			new Position( doc.graveyard, [ 0 ] ),
-			doc.version
-		);
-
-		expect( op.type ).to.equal( 'remove' );
-	} );
-
-	it( 'should extend MoveOperation class', () => {
-		const operation = new RemoveOperation(
-			new Position( root, [ 2 ] ),
-			2,
-			new Position( doc.graveyard, [ 0 ] ),
-			doc.version
-		);
-
-		expect( operation ).to.be.instanceof( MoveOperation );
-	} );
-
-	it( 'should be able to remove set of nodes and append them to graveyard root', () => {
-		root._insertChild( 0, new Text( 'fozbar' ) );
-
-		model.applyOperation(
-			new RemoveOperation(
-				new Position( root, [ 2 ] ),
-				2,
-				new Position( doc.graveyard, [ 0 ] ),
-				doc.version
-			)
-		);
-
-		expect( doc.version ).to.equal( 1 );
-		expect( root.maxOffset ).to.equal( 4 );
-		expect( root.getChild( 0 ).data ).to.equal( 'foar' );
-
-		expect( graveyard.maxOffset ).to.equal( 2 );
-		expect( graveyard.getChild( 0 ).data ).to.equal( 'zb' );
-	} );
-
-	it( 'should create RemoveOperation with same parameters when cloned', () => {
-		const pos = new Position( root, [ 2 ] );
-
-		const operation = new RemoveOperation( pos, 2, new Position( doc.graveyard, [ 0 ] ), doc.version );
-		const clone = operation.clone();
-
-		expect( clone ).to.be.instanceof( RemoveOperation );
-		expect( clone.sourcePosition.isEqual( pos ) ).to.be.true;
-		expect( clone.targetPosition.isEqual( operation.targetPosition ) ).to.be.true;
-		expect( clone.howMany ).to.equal( operation.howMany );
-		expect( clone.baseVersion ).to.equal( operation.baseVersion );
-	} );
-
-	it( 'should create ReinsertOperation when reversed', () => {
-		const position = new Position( root, [ 0 ] );
-		const operation = new RemoveOperation( position, 2, new Position( doc.graveyard, [ 0 ] ), 0 );
-		const reverse = operation.getReversed();
-
-		expect( reverse ).to.be.an.instanceof( ReinsertOperation );
-		expect( reverse.baseVersion ).to.equal( 1 );
-		expect( reverse.howMany ).to.equal( 2 );
-		expect( reverse.sourcePosition.isEqual( operation.targetPosition ) ).to.be.true;
-		expect( reverse.targetPosition.isEqual( position ) ).to.be.true;
-	} );
-
-	it( 'should create correct ReinsertOperation when reversed if source range was in graveyard', () => {
-		const operation = new RemoveOperation( new Position( doc.graveyard, [ 2 ] ), 1, new Position( doc.graveyard, [ 0 ] ), 0 );
-		const reverse = operation.getReversed();
-
-		expect( reverse.sourcePosition.path ).to.deep.equal( [ 0 ] );
-		expect( reverse.targetPosition.path ).to.deep.equal( [ 3 ] );
-	} );
-
-	it( 'should undo remove set of nodes by applying reverse operation', () => {
-		const position = new Position( root, [ 0 ] );
-		const operation = new RemoveOperation( position, 3, new Position( doc.graveyard, [ 0 ] ), 0 );
-		const reverse = operation.getReversed();
-
-		root._insertChild( 0, new Text( 'bar' ) );
-
-		model.applyOperation( operation );
-
-		expect( doc.version ).to.equal( 1 );
-		expect( root.maxOffset ).to.equal( 0 );
-
-		model.applyOperation( reverse );
-
-		expect( doc.version ).to.equal( 2 );
-		expect( root.maxOffset ).to.equal( 3 );
-		expect( root.getChild( 0 ).data ).to.equal( 'bar' );
-	} );
-
-	it( 'should properly remove a node that is already in a graveyard', () => {
-		doc.graveyard._appendChild( [ new Element( 'x' ), new Element( 'y' ), new Element( 'z' ) ] );
-
-		const position = new Position( doc.graveyard, [ 2 ] );
-		const operation = new RemoveOperation( position, 1, new Position( doc.graveyard, [ 0 ] ), 0 );
-
-		model.applyOperation( operation );
-
-		expect( doc.graveyard.childCount ).to.equal( 3 );
-		expect( doc.graveyard.getChild( 0 ).name ).to.equal( 'z' );
-		expect( doc.graveyard.getChild( 1 ).name ).to.equal( 'x' );
-		expect( doc.graveyard.getChild( 2 ).name ).to.equal( 'y' );
-	} );
-
-	describe( '_validate()', () => {
-		it( 'should throw when is executed on detached item', () => {
-			const docFrag = new DocumentFragment();
-			const item = new Element( 'foo' );
-
-			docFrag._appendChild( [ item ] );
-
-			const op = new RemoveOperation(
-				new Position( docFrag, [ 0 ] ),
-				1,
-				new Position( doc.graveyard, [ 0 ] ),
-				doc.version
-			);
-
-			expect( () => {
-				op._validate();
-			} ).to.throw( CKEditorError, /^remove-operation-on-detached-item/ );
-		} );
-	} );
-
-	describe( 'toJSON', () => {
-		it( 'should create proper json object', () => {
-			const op = new RemoveOperation(
-				new Position( root, [ 2 ] ),
-				2,
-				new Position( doc.graveyard, [ 0 ] ),
-				doc.version
-			);
-
-			const serialized = jsonParseStringify( op );
-
-			expect( serialized ).to.deep.equal( {
-				__className: 'engine.model.operation.RemoveOperation',
-				baseVersion: 0,
-				howMany: 2,
-				sourcePosition: jsonParseStringify( op.sourcePosition ),
-				targetPosition: jsonParseStringify( op.targetPosition )
-			} );
-		} );
-	} );
-
-	describe( 'fromJSON', () => {
-		it( 'should create proper RemoveOperation from json object', () => {
-			const op = new RemoveOperation(
-				new Position( root, [ 2 ] ),
-				2,
-				new Position( doc.graveyard, [ 0 ] ),
-				doc.version
-			);
-
-			const serialized = jsonParseStringify( op );
-			const deserialized = RemoveOperation.fromJSON( serialized, doc );
-
-			expect( deserialized ).to.deep.equal( op );
-		} );
-	} );
-} );
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index fc1f222f6..0087152bd 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -16,7 +16,6 @@ import AttributeOperation from '../../../src/model/operation/attributeoperation'
 import RootAttributeOperation from '../../../src/model/operation/rootattributeoperation';
 import MarkerOperation from '../../../src/model/operation/markeroperation';
 import MoveOperation from '../../../src/model/operation/moveoperation';
-import RemoveOperation from '../../../src/model/operation/removeoperation';
 import RenameOperation from '../../../src/model/operation/renameoperation';
 import NoOperation from '../../../src/model/operation/nooperation';
 
@@ -688,7 +687,7 @@ describe( 'transform', () => {
 			} );
 		} );
 
-		describe( 'by RemoveOperation', () => {
+		describe( 'by MoveOperation to graveyard', () => {
 			beforeEach( () => {
 				start = new Position( doc.graveyard, [ 2, 0 ] );
 				end = new Position( doc.graveyard, [ 2, 4 ] );
@@ -701,7 +700,7 @@ describe( 'transform', () => {
 			} );
 
 			it( 'remove operation inserted elements before attribute operation range: increment path', () => {
-				const transformBy = new RemoveOperation(
+				const transformBy = new MoveOperation(
 					new Position( root, [ 0 ] ),
 					2,
 					new Position( doc.graveyard, [ 0 ] ),
@@ -721,7 +720,7 @@ describe( 'transform', () => {
 			} );
 
 			it( 'remove operation inserted elements after attribute operation range: do nothing', () => {
-				const transformBy = new RemoveOperation(
+				const transformBy = new MoveOperation(
 					new Position( root, [ 0 ] ),
 					2,
 					new Position( doc.graveyard, [ 0 ] ),
@@ -1962,11 +1961,11 @@ describe( 'transform', () => {
 			} );
 		} );
 
-		describe( 'by RemoveOperation', () => {
+		describe( 'by MoveOperation to graveyard', () => {
 			let transformBy;
 
 			beforeEach( () => {
-				transformBy = new RemoveOperation(
+				transformBy = new MoveOperation(
 					Position.createFromPosition( op.sourcePosition ),
 					op.howMany,
 					new Position( doc.graveyard, [ 0 ] ),
@@ -1974,7 +1973,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it( 'should skip context.aIsStrong and be less important than RemoveOperation', () => {
+			it( 'should skip context.aIsStrong and be less important than MoveOperation', () => {
 				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
 
 				expect( transOp.length ).to.equal( 1 );
@@ -2020,10 +2019,10 @@ describe( 'transform', () => {
 		} );
 	} );
 
-	describe( 'RemoveOperation', () => {
+	describe( 'MoveOperation to graveyard', () => {
 		describe( 'by MoveOperation', () => {
 			it( 'should force removing content even if was less important', () => {
-				const op = new RemoveOperation( new Position( root, [ 8 ] ), 2, new Position( doc.graveyard, [ 0 ] ), 0 );
+				const op = new MoveOperation( new Position( root, [ 8 ] ), 2, new Position( doc.graveyard, [ 0 ] ), 0 );
 
 				const targetPosition = Position.createFromPosition( op.targetPosition );
 
@@ -2036,7 +2035,7 @@ describe( 'transform', () => {
 				expect( transOp.length ).to.equal( 1 );
 
 				expectOperation( transOp[ 0 ], {
-					type: RemoveOperation,
+					type: MoveOperation,
 					howMany: 2,
 					sourcePosition,
 					targetPosition
diff --git a/tests/model/range.js b/tests/model/range.js
index feea61f39..2f7bfbcac 100644
--- a/tests/model/range.js
+++ b/tests/model/range.js
@@ -12,7 +12,6 @@ import TreeWalker from '../../src/model/treewalker';
 import AttributeOperation from '../../src/model/operation/attributeoperation';
 import InsertOperation from '../../src/model/operation/insertoperation';
 import MoveOperation from '../../src/model/operation/moveoperation';
-import RemoveOperation from '../../src/model/operation/removeoperation';
 import RenameOperation from '../../src/model/operation/renameoperation';
 import MergeOperation from '../../src/model/operation/mergeoperation';
 import SplitOperation from '../../src/model/operation/splitoperation';
@@ -898,10 +897,10 @@ describe( 'Range', () => {
 			} );
 		} );
 
-		describe( 'by RemoveOperation', () => {
+		describe( 'by MoveOperation to graveyard', () => {
 			it( 'remove before range', () => {
 				const start = new Position( root, [ 0 ] );
-				const op = new RemoveOperation( start, 2, gyPos, 1 );
+				const op = new MoveOperation( start, 2, gyPos, 1 );
 
 				const transformed = range.getTransformedByOperation( op );
 
@@ -910,7 +909,7 @@ describe( 'Range', () => {
 
 			it( 'remove intersecting with range', () => {
 				const start = new Position( root, [ 4 ] );
-				const op = new RemoveOperation( start, 2, gyPos, 1 );
+				const op = new MoveOperation( start, 2, gyPos, 1 );
 
 				const transformed = range.getTransformedByOperation( op );
 
@@ -922,7 +921,7 @@ describe( 'Range', () => {
 			it( 'remove inside the range', () => {
 				const start = new Position( root, [ 3 ] );
 
-				const op = new RemoveOperation( start, 2, gyPos, 1 );
+				const op = new MoveOperation( start, 2, gyPos, 1 );
 
 				const transformed = range.getTransformedByOperation( op );
 
diff --git a/tests/model/writer.js b/tests/model/writer.js
index e31a5d0a4..fd466b90e 100644
--- a/tests/model/writer.js
+++ b/tests/model/writer.js
@@ -1545,7 +1545,7 @@ describe( 'Writer', () => {
 				expect( batch.operations.length ).to.equal( 2 );
 			} );
 
-			it( 'should use RemoveOperation', () => {
+			it( 'should use MoveOperation to graveyard', () => {
 				batch = new Batch();
 				remove( div );
 

From a120c857ba78033579cf3b84f0d7436d543d0179 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 14:27:10 +0200
Subject: [PATCH 09/26] Fixed: Fixed results of `Range#getTransformedByMerge`
 for edge cases.

---
 src/model/operation/transform.js          |  6 ++++
 src/model/position.js                     |  2 ++
 src/model/range.js                        | 33 +++++++++++++++++----
 tests/model/operation/transform/marker.js | 35 +++++++++++++++++++++++
 4 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index f0a9dba73..dc8e59dc0 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -1156,6 +1156,12 @@ setTransformation( RenameOperation, InsertOperation, ( a, b ) => {
 } );
 
 setTransformation( RenameOperation, MergeOperation, ( a, b ) => {
+	if ( a.position.isEqual( b.deletionPosition ) ) {
+		a.position = Position.createFromPosition( b.graveyardPosition );
+
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByMergeOperation( b );
 
 	return [ a ];
diff --git a/src/model/position.js b/src/model/position.js
index 7b3cfa5a4..9c5f06057 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -563,6 +563,8 @@ export default class Position {
 				// Above happens during OT when the merged element is moved before the merged-to element.
 				pos = pos._getTransformedByDeletion( operation.deletionPosition, 1 );
 			}
+		} else if ( this.isEqual( operation.deletionPosition ) ) {
+			pos = Position.createFromPosition( operation.deletionPosition );
 		} else {
 			pos = this._getTransformedByMove( operation.deletionPosition, operation.graveyardPosition, 1 );
 		}
diff --git a/src/model/range.js b/src/model/range.js
index 4dc795e90..30746b6af 100644
--- a/src/model/range.js
+++ b/src/model/range.js
@@ -493,16 +493,37 @@ export default class Range {
 	}
 
 	_getTransformedByMergeOperation( operation ) {
-		const start = this.start._getTransformedByMergeOperation( operation );
-		const end = this.end._getTransformedByMergeOperation( operation );
+		let start = this.start._getTransformedByMergeOperation( operation );
+		let end = this.end._getTransformedByMergeOperation( operation );
 
 		if ( start.isAfter( end ) ) {
-			// This happens in the following case:
+			// This happens in the following two, similar cases:
 			//
-			// <p>abc</p>{<p>x}yz</p> -> <p>abcx}yz</p>{
-			//                           <p>abcx{yz</p>}
+			// Case 1: Range start is directly before merged node.
+			//         Resulting range should include only nodes from the merged element:
 			//
-			return new Range( end, start );
+			// Before: <p>aa</p>{<p>b}b</p><p>cc</p>
+			// Merge:  <p>aab}b</p>{<p>cc</p>
+			// Fix:    <p>aa{b}b</p><p>cc</p>
+			//
+			// Case 2: Range start is not directly before merged node.
+			//         Result should include all nodes that were in the original range.
+			//
+			// Before: <p>aa</p>{<p>cc</p><p>b}b</p>
+			// Merge:  <p>aab}b</p>{<p>cc</p>
+			// Fix:    <p>aa{bb</p><p>cc</p>}
+			//
+			//         The range is expanded by an additional `b` letter but it is better than dropping the whole `cc` paragraph.
+			//
+			if ( !operation.deletionPosition.isEqual( start ) ) {
+				// Case 2.
+				end = operation.deletionPosition;
+			}
+
+			// In both cases start is at the end of the merge-to element.
+			start = operation.targetPosition;
+
+			return new Range( start, end );
 		}
 
 		return new Range( start, end );
diff --git a/tests/model/operation/transform/marker.js b/tests/model/operation/transform/marker.js
index 07b4a2f2b..0b2fe0c78 100644
--- a/tests/model/operation/transform/marker.js
+++ b/tests/model/operation/transform/marker.js
@@ -789,6 +789,41 @@ describe( 'transform', () => {
 					'</blockQuote>'
 				);
 			} );
+
+			it( 'only marker end is inside merged element #1', () => {
+				john.setData( '<paragraph>Foo</paragraph>[<paragraph>B]ar</paragraph>' );
+				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
+
+				john.setMarker( 'm1' );
+				kate.merge();
+
+				syncClients();
+
+				expectClients( '<paragraph>Foo<m1:start></m1:start>B<m1:end></m1:end>ar</paragraph>' );
+			} );
+
+			it( 'only marker end is inside merged element #2', () => {
+				john.setData( '<paragraph>Foo[]Bar</paragraph>' );
+				kate.setData( '<paragraph>Foo[]Bar</paragraph>' );
+
+				kate.split();
+
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
+
+				john.setSelection( [ 1 ] );
+				john.insert( '<paragraph>Xyz</paragraph>' );
+
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Xyz</paragraph><paragraph>Bar</paragraph>' );
+
+				john.setSelection( [ 1 ], [ 2, 1 ] );
+				john.setMarker( 'm1' );
+				kate.undo();
+
+				syncClients();
+				expectClients( '<paragraph>Foo<m1:start></m1:start>Bar</paragraph><paragraph>Xyz</paragraph><m1:end></m1:end>' );
+			} );
 		} );
 
 		describe( 'by rename', () => {

From 977c81ef7e24e61f2443a1330fa3f10488cf5747 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 15:46:07 +0200
Subject: [PATCH 10/26] Changed: `context.wasUndone` changed from function to
 properties.

---
 src/model/operation/transform.js | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index f0a9dba73..12f8db766 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -113,13 +113,17 @@ function transformSets( operationsA, operationsB, options ) {
 					const opA = opsA[ k ];
 					const opB = opsB[ l ];
 
-					context.aIsStrong = true;
-					const newOpA = transform( opA, opB, context );
-
-					context.aIsStrong = false;
-					const newOpB = transform( opB, opA, context );
-
-					delete context.aIsStrong;
+					const newOpA = transform( opA, opB, {
+						aIsStrong: true,
+						aWasUndone: context.wasUndone( opA ),
+						bWasUndone: context.wasUndone( opB )
+					} );
+
+					const newOpB = transform( opB, opA, {
+						aIsStrong: false,
+						aWasUndone: context.wasUndone( opB ),
+						bWasUndone: context.wasUndone( opA ),
+					} );
 
 					if ( options.useContext ) {
 						updateOriginalOperation( context, opA, newOpA );
@@ -269,7 +273,7 @@ setTransformation( AttributeOperation, InsertOperation, ( a, b ) => {
 		// <p>Fo[zb]ar<p>
 		//
 		// New text with `highlight="red"` is typed:
-		// <p>Fo[z<$text higlight="red">x</$text>a]r</p>
+		// <p>Fo[z<$text highlight="red">x</$text>a]r</p>
 		//
 		// In this case three operations are needed: `oldValue=null, newValue="yellow"` for `z`, `oldValue="red",
 		// newValue="yellow"` for `x` and `oldValue=null, newValue="yellow"` for `a`. It could even happen that
@@ -707,7 +711,7 @@ setTransformation( MergeOperation, MoveOperation, ( a, b, context ) => {
 	//
 	const removedRange = Range.createFromPositionAndShift( b.sourcePosition, b.howMany );
 
-	if ( b instanceof RemoveOperation && !context.wasUndone( b ) ) {
+	if ( b instanceof RemoveOperation && !context.bWasUndone ) {
 		if ( a.deletionPosition.hasSameParentAs( b.sourcePosition ) && removedRange.containsPosition( a.sourcePosition ) ) {
 			return getNoOp();
 		}
@@ -1057,7 +1061,7 @@ setTransformation( MoveOperation, MergeOperation, ( a, b, context ) => {
 			//			deleting it was to have it all deleted. From user experience point of view, moving back the
 			//			removed nodes might be unexpected. This means that in this scenario we will reverse merging and remove the element.
 			//
-			if ( !context.wasUndone( a ) ) {
+			if ( !context.aWasUndone ) {
 				return [ b.getReversed(), a ];
 			}
 		} else {

From e30d09d5d1a626a2a960befcc2a81044976d7284 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Fri, 27 Jul 2018 11:20:11 +0200
Subject: [PATCH 11/26] Changed: Introduced relations in OT.

---
 src/model/operation/transform.js             | 303 ++++++++++++++++---
 src/model/position.js                        |   1 +
 tests/model/operation/transform.js           |  42 +--
 tests/model/operation/transform/attribute.js |   2 +-
 tests/model/operation/transform/insert.js    |   4 +-
 tests/model/operation/transform/marker.js    |   4 +-
 tests/model/operation/transform/move.js      |   8 +-
 tests/model/operation/transform/remove.js    |  12 +-
 tests/model/operation/transform/split.js     |  27 +-
 tests/model/operation/transform/unwrap.js    |   5 +-
 tests/model/operation/transform/utils.js     |  42 ++-
 tests/model/operation/transform/wrap.js      |  52 +++-
 12 files changed, 377 insertions(+), 125 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index 12f8db766..c8249cdcf 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -72,7 +72,7 @@ function updateBaseVersions( operations, baseVersion ) {
 	return operations;
 }
 
-function transform( a, b, context = { aIsStrong: false } ) {
+function transform( a, b, context = { aIsStrong: false, wasUndone: () => false, getRelation: () => null } ) {
 	const transformationFunction = getTransformation( a, b );
 
 	return transformationFunction( a.clone(), b, context );
@@ -128,6 +128,8 @@ function transformSets( operationsA, operationsB, options ) {
 					if ( options.useContext ) {
 						updateOriginalOperation( context, opA, newOpA );
 						updateOriginalOperation( context, opB, newOpB );
+
+						updateRelations( context, opA, opB );
 					}
 
 					opsA.splice( k, 1, ...newOpA );
@@ -180,6 +182,7 @@ function initializeContext( opsA, opsB, options ) {
 	}
 
 	context.document = options.document;
+	context.relations = new Map();
 
 	context.wasUndone = function( op ) {
 		if ( !options.useContext ) {
@@ -191,9 +194,151 @@ function initializeContext( opsA, opsB, options ) {
 		return this.document.history.isUndoneOperation( originalOp );
 	};
 
+	context.getRelation = function( opA, opB ) {
+		if ( !options.useContext ) {
+			return null;
+		}
+
+		const origB = this.originalOperations.get( opB );
+		const undoneB = this.document.history.getUndoneOperation( origB );
+
+		if ( !undoneB ) {
+			return null;
+		}
+
+		const origA = this.originalOperations.get( opA );
+		const relationsA = this.relations.get( origA );
+
+		if ( relationsA ) {
+			return relationsA.get( undoneB ) || null;
+		}
+
+		return null;
+	};
+
 	return context;
 }
 
+function updateRelations( context, opA, opB ) {
+	switch ( opA.constructor ) {
+		case MoveOperation:
+		case RemoveOperation:
+		case ReinsertOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.targetPosition.isEqual( opB.sourcePosition ) || opB.movedRange.containsPosition( opA.targetPosition ) ) {
+						setRelation( context, opA, opB, 'insertAtSource' );
+						setRelation( context, opB, opA, 'splitBefore' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.targetPosition.isEqual( opB.sourcePosition ) || opA.targetPosition.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'insertBefore' );
+						setRelation( context, opB, opA, 'insertAfter' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.targetPosition.hasSameParentAs( opB.targetPosition );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'insertInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+
+		case SplitOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'splitBefore' );
+						setRelation( context, opB, opA, 'splitAfter' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'splitBefore' );
+						setRelation( context, opB, opA, 'insertAtSource' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.position.hasSameParentAs( opB.position );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'splitInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+
+		case InsertOperation: {
+			switch ( opB.constructor ) {
+				case MergeOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opB.movedRange.containsPosition( opA.position ) ) {
+						setRelation( context, opA, opB, 'insertAtSource' );
+					}
+
+					break;
+				}
+
+				case MoveOperation: {
+					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
+						setRelation( context, opA, opB, 'insertBefore' );
+					}
+
+					break;
+				}
+
+				case UnwrapOperation: {
+					const isInside = opA.position.hasSameParentAs( opB.position );
+
+					if ( isInside ) {
+						setRelation( context, opA, opB, 'insertInside' );
+					}
+
+					break;
+				}
+			}
+
+			break;
+		}
+	}
+}
+
+function setRelation( context, opA, opB, relation ) {
+	const origA = context.originalOperations.get( opA );
+	const origB = context.originalOperations.get( opB );
+
+	let relationsA = context.relations.get( origA );
+
+	if ( !relationsA ) {
+		relationsA = new Map();
+		context.relations.set( origA, relationsA );
+	}
+
+	relationsA.set( origB, relation );
+}
+
 function updateOriginalOperation( context, oldOp, newOps ) {
 	const originalOp = context.originalOperations.get( oldOp );
 
@@ -349,8 +494,12 @@ setTransformation( AttributeOperation, MergeOperation, ( a, b ) => {
 
 	// Case 1:	Attribute change on the merged element. In this case, the merged element was moved to graveyard.
 	//			An additional attribute operation that will change the (re)moved element needs to be generated.
+	//			Do it only, if there is more than one element in attribute range. If there is only one element,
+	//			it will be handled by the default algorithm.
 	//
-	if ( a.range.start.hasSameParentAs( b.deletionPosition ) ) {
+	const howMany = a.range.end.offset - a.range.start.offset;
+
+	if ( howMany > 1 && a.range.start.hasSameParentAs( b.deletionPosition ) ) {
 		if ( a.range.containsPosition( b.deletionPosition ) || a.range.start.isEqual( b.deletionPosition ) ) {
 			ranges.push( Range.createFromPositionAndShift( b.graveyardPosition, 1 ) );
 		}
@@ -545,13 +694,23 @@ setTransformation( InsertOperation, InsertOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, MoveOperation, ( a, b ) => {
+setTransformation( InsertOperation, MoveOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'insertBefore' ) {
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByMoveOperation( b );
 
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, SplitOperation, ( a, b ) => {
+setTransformation( InsertOperation, SplitOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+		a.position = b.moveTargetPosition;
+
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedBySplitOperation( b );
 
 	return [ a ];
@@ -563,7 +722,13 @@ setTransformation( InsertOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( InsertOperation, WrapOperation, ( a, b ) => {
+setTransformation( InsertOperation, WrapOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+		a.position = b.targetPosition;
+
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByWrapOperation( b );
 
 	return [ a ];
@@ -720,7 +885,7 @@ setTransformation( MergeOperation, MoveOperation, ( a, b, context ) => {
 	a.sourcePosition = a.sourcePosition._getTransformedByMoveOperation( b );
 	a.targetPosition = a.targetPosition._getTransformedByMoveOperation( b );
 
-	if ( !a.graveyardPosition.isEqual( b.targetPosition ) || !context.aIsStrong ) {
+	if ( !a.graveyardPosition.isEqual( b.targetPosition ) ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
@@ -751,9 +916,9 @@ setTransformation( MergeOperation, SplitOperation, ( a, b ) => {
 	//			There is one exception though - when the split operation is a result of undo. In those cases, it is needed
 	//			to keep `targetPosition` intact, so the nodes are returned to the correct element.
 	//
-	if ( a.targetPosition.isEqual( b.position ) && b.graveyardPosition ) {
-		return [ a ];
-	}
+	// if ( a.targetPosition.isEqual( b.position ) && b.graveyardPosition ) {
+	// 	return [ a ];
+	// }
 
 	a.targetPosition = a.targetPosition._getTransformedBySplitOperation( b );
 
@@ -818,14 +983,14 @@ setTransformation( MergeOperation, UnwrapOperation, ( a, b, context ) => {
 
 // -----------------------
 
-setTransformation( MoveOperation, InsertOperation, ( a, b ) => {
+setTransformation( MoveOperation, InsertOperation, ( a, b, context ) => {
 	const moveRange = Range.createFromPositionAndShift( a.sourcePosition, a.howMany );
 	const transformed = moveRange._getTransformedByInsertOperation( b, false )[ 0 ];
 
 	a.sourcePosition = transformed.start;
 	a.howMany = transformed.end.offset - transformed.start.offset;
 
-	if ( !a.targetPosition.isEqual( b.position ) ) {
+	if ( !a.targetPosition.isEqual( b.position ) || context.getRelation( b, a ) == 'insertBefore' ) {
 		a.targetPosition = a.targetPosition._getTransformedByInsertOperation( b );
 	}
 
@@ -842,14 +1007,23 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 
 	// Assign `context.aIsStrong` to a different variable, because the value may change during execution of
 	// this algorithm and we do not want to override original `context.aIsStrong` that will be used in later transformations.
-	let aIsStrong = context.aIsStrong;
+	let aIsStrong = context.aIsStrong || context.getRelation( a, b ) == 'insertBefore';
 
 	// `a.targetPosition` could be affected by the `b` operation. We will transform it.
-	const newTargetPosition = a.targetPosition._getTransformedByMove(
-		b.sourcePosition,
-		b.targetPosition,
-		b.howMany
-	);
+	let newTargetPosition;
+
+	if ( a.targetPosition.isEqual( b.targetPosition ) && aIsStrong ) {
+		newTargetPosition = a.targetPosition._getTransformedByDeletion(
+			b.sourcePosition,
+			b.howMany
+		);
+	} else {
+		newTargetPosition = a.targetPosition._getTransformedByMove(
+			b.sourcePosition,
+			b.targetPosition,
+			b.howMany
+		);
+	}
 
 	//
 	// Special case #1 + mirror.
@@ -997,7 +1171,7 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 	return makeMoveOperationsFromRanges( ranges, newTargetPosition );
 } );
 
-setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
+setTransformation( MoveOperation, SplitOperation, ( a, b, context ) => {
 	const newTargetPosition = a.targetPosition._getTransformedBySplitOperation( b );
 
 	// Case 1:	Last element in the moved range got split.
@@ -1032,8 +1206,8 @@ setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
 		rightRange = rightRange._getTransformedBySplitOperation( b );
 
 		const ranges = [
-			rightRange,
-			Range.createFromPositionAndShift( moveRange.start, b.position.offset - moveRange.start.offset )
+			new Range( moveRange.start, b.position ),
+			rightRange
 		];
 
 		return makeMoveOperationsFromRanges( ranges, newTargetPosition );
@@ -1047,6 +1221,10 @@ setTransformation( MoveOperation, SplitOperation, ( a, b ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
+	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+		a.targetPosition = b.targetPosition;
+	}
+
 	return [ a ];
 } );
 
@@ -1085,7 +1263,7 @@ setTransformation( MoveOperation, MergeOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( MoveOperation, WrapOperation, ( a, b ) => {
+setTransformation( MoveOperation, WrapOperation, ( a, b, context ) => {
 	const moveRange = Range.createFromPositionAndShift( a.sourcePosition, a.howMany );
 	const newTargetPosition = a.targetPosition._getTransformedByWrapOperation( b );
 
@@ -1137,6 +1315,10 @@ setTransformation( MoveOperation, WrapOperation, ( a, b ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
+	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+		a.targetPosition = b.targetPosition;
+	}
+
 	return [ a ];
 } );
 
@@ -1239,7 +1421,11 @@ setTransformation( RootAttributeOperation, RootAttributeOperation, ( a, b, conte
 
 // -----------------------
 
-setTransformation( SplitOperation, InsertOperation, ( a, b ) => {
+setTransformation( SplitOperation, InsertOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertAtSource' ) {
+		return [ a ];
+	}
+
 	a.position = a.position._getTransformedByInsertOperation( b );
 
 	return [ a ];
@@ -1255,7 +1441,7 @@ setTransformation( SplitOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
+setTransformation( SplitOperation, MoveOperation, ( a, b, context ) => {
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
@@ -1283,6 +1469,12 @@ setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
 		return [ a ];
 	}
 
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+		a.position = a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
+
+		return [ a ];
+	}
+
 	// The default case.
 	//
 	a.position = a.position._getTransformedByMoveOperation( b );
@@ -1290,7 +1482,7 @@ setTransformation( SplitOperation, MoveOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
+setTransformation( SplitOperation, SplitOperation, ( a, b, context ) => {
 	if ( a.position.isEqual( b.position ) ) {
 		if ( !a.graveyardPosition && !b.graveyardPosition ) {
 			return getNoOp();
@@ -1299,6 +1491,8 @@ setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
 		if ( a.graveyardPosition && b.graveyardPosition && a.graveyardPosition.isEqual( b.graveyardPosition ) ) {
 			return getNoOp();
 		}
+	} else if ( a.position.isEqual( b.insertionPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+		return [ a ];
 	} else {
 		a.position = a.position._getTransformedBySplitOperation( b );
 	}
@@ -1310,7 +1504,7 @@ setTransformation( SplitOperation, SplitOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
+setTransformation( SplitOperation, WrapOperation, ( a, b, context ) => {
 	// Case 1:	If split position has been wrapped, reverse the wrapping so that split can be applied as intended.
 	//			This is an edge case scenario where it is difficult to find a correct solution.
 	//			Since it will be a rare (or only theoretical) scenario, the algorithm will perform the easy solution.
@@ -1328,7 +1522,11 @@ setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
 		return [ reversed, a ];
 	}
 
-	a.position = a.position._getTransformedByWrapOperation( b );
+	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'splitInside' ) {
+		a.position = b.targetPosition;
+	} else {
+		a.position = a.position._getTransformedByWrapOperation( b );
+	}
 
 	if ( a.graveyardPosition && b.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByDeletion( b.graveyardPosition, 1 );
@@ -1337,8 +1535,17 @@ setTransformation( SplitOperation, WrapOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( SplitOperation, UnwrapOperation, ( a, b ) => {
-	a.position = a.position._getTransformedByUnwrapOperation( b );
+setTransformation( SplitOperation, UnwrapOperation, ( a, b, context ) => {
+	const splitInside = a.position.hasSameParentAs( b.position );
+
+	if ( splitInside && !context.wasUndone( b ) ) {
+		const path = b.graveyardPosition.path.slice();
+		path.push( 0 );
+
+		a.position = new Position( b.graveyardPosition.root, path );
+	} else {
+		a.position = a.position._getTransformedByUnwrapOperation( b );
+	}
 
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByInsertion( b.graveyardPosition, 1 );
@@ -1349,7 +1556,13 @@ setTransformation( SplitOperation, UnwrapOperation, ( a, b ) => {
 
 // -----------------------
 
-setTransformation( WrapOperation, InsertOperation, ( a, b ) => {
+setTransformation( WrapOperation, InsertOperation, ( a, b, context ) => {
+	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertInside' ) {
+		a.howMany += b.howMany;
+
+		return [ a ];
+	}
+
 	const transformed = a.wrappedRange._getTransformedByInsertOperation( b, false )[ 0 ];
 
 	a.position = transformed.start;
@@ -1371,11 +1584,18 @@ setTransformation( WrapOperation, MergeOperation, ( a, b ) => {
 	return [ a ];
 } );
 
-setTransformation( WrapOperation, MoveOperation, ( a, b ) => {
+setTransformation( WrapOperation, MoveOperation, ( a, b, context ) => {
 	if ( a.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
+	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( b, a ) == 'insertInside' ) {
+		a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
+		a.howMany += b.howMany;
+
+		return [ a ];
+	}
+
 	const ranges = breakRangeByMoveOperation( a.wrappedRange, b, false );
 
 	if ( ranges.length == 0 ) {
@@ -1392,10 +1612,14 @@ setTransformation( WrapOperation, MoveOperation, ( a, b ) => {
 	} );
 } );
 
-setTransformation( WrapOperation, SplitOperation, ( a, b ) => {
+setTransformation( WrapOperation, SplitOperation, ( a, b, context ) => {
 	// Case 1:	If range to wrap got split by split operation cancel the wrapping.
+	//			Do that only if this is not undo mode. If `b` operation was earlier transformed by unwrap operation
+	//			and the split position was inside the unwrapped range, then proceed without special case.
 	//
-	if ( a.position.hasSameParentAs( b.position ) && a.wrappedRange.containsPosition( b.position ) ) {
+	const isInside = a.position.hasSameParentAs( b.position ) && a.wrappedRange.containsPosition( b.position );
+
+	if ( isInside && context.getRelation( b, a ) !== 'splitInside' ) {
 		// We cannot just return no-op in this case, because in the mirror case scenario the wrap is reversed, which
 		// might introduce a new node in the graveyard (if the wrap didn't have `graveyardPosition`, then the wrap
 		// created a new element which was put to the graveyard when the wrap was reversed).
@@ -1405,7 +1629,7 @@ setTransformation( WrapOperation, SplitOperation, ( a, b ) => {
 			const graveyard = a.position.root.document.graveyard;
 			const graveyardPosition = new Position( graveyard, [ 0 ] );
 
-			return new InsertOperation( graveyardPosition, a.element, 0 );
+			return [ new InsertOperation( graveyardPosition, a.element, 0 ) ];
 		} else {
 			return getNoOp();
 		}
@@ -1626,7 +1850,7 @@ setTransformation( UnwrapOperation, MergeOperation, ( a, b, context ) => {
 	return [ a ];
 } );
 
-setTransformation( UnwrapOperation, MoveOperation, ( a, b, context ) => {
+setTransformation( UnwrapOperation, MoveOperation, ( a, b ) => {
 	// Case 1:	Move operation moves nodes from the unwrapped element.
 	//			This does not have any impact on `UnwrapOperation#position`, but `#howMany` has to be changed.
 	//
@@ -1644,7 +1868,7 @@ setTransformation( UnwrapOperation, MoveOperation, ( a, b, context ) => {
 
 	a.position = a.position._getTransformedByMoveOperation( b );
 
-	if ( !a.graveyardPosition.isEqual( b.targetPosition ) || !context.aIsStrong ) {
+	if ( !a.graveyardPosition.isEqual( b.targetPosition ) ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
@@ -1695,6 +1919,10 @@ setTransformation( UnwrapOperation, WrapOperation, ( a, b ) => {
 		a.howMany = a.howMany - b.howMany + 1;
 	}
 
+	if ( b.graveyardPosition && compareArrays( a.position.getParentPath(), b.graveyardPosition.path ) == 'same' ) {
+		a.howMany = b.howMany;
+	}
+
 	// The default case.
 	//
 	a.position = a.position._getTransformedByWrapOperation( b );
@@ -1713,6 +1941,8 @@ setTransformation( UnwrapOperation, UnwrapOperation, ( a, b, context ) => {
 		a.position = new Position( b.graveyardPosition.root, path );
 		a.howMany = 0;
 		a.graveyardPosition = Position.createFromPosition( b.graveyardPosition );
+
+		return [ a ];
 	}
 
 	a.position = a.position._getTransformedByUnwrapOperation( b );
@@ -1763,8 +1993,7 @@ function makeMoveOperationsFromRanges( ranges, targetPosition ) {
 			ranges[ j ] = ranges[ j ]._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany )[ 0 ];
 		}
 
-		// targetPosition.stickiness = 'toPrevious';
-		targetPosition = targetPosition._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany, true );
+		targetPosition = targetPosition._getTransformedByMove( op.sourcePosition, op.targetPosition, op.howMany );
 	}
 
 	return operations;
diff --git a/src/model/position.js b/src/model/position.js
index 7b3cfa5a4..4a91b11f9 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -761,6 +761,7 @@ export default class Position {
 
 		// The first part of a path to combined position is a path to the place where nodes were moved.
 		const combined = Position.createFromPosition( target );
+		combined.stickiness = this.stickiness;
 
 		// Then we have to update the rest of the path.
 
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index fc1f222f6..d90a85111 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -53,6 +53,12 @@ describe( 'transform', () => {
 		}
 	}
 
+	const contextIsStrong = {
+		aIsStrong: true,
+		wasUndone: () => false,
+		getRelation: () => false
+	};
+
 	describe( 'InsertOperation', () => {
 		let nodeC, nodeD, position;
 
@@ -119,7 +125,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -310,7 +316,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -862,7 +868,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.oldValue = 'xyz';
 
@@ -1102,7 +1108,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1241,7 +1247,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1567,7 +1573,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.sourcePosition.path = [ 4, 1, 0 ];
 
@@ -1599,7 +1605,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.sourcePosition.path = [ 4, 1, 1 ];
 
@@ -1637,7 +1643,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1675,7 +1681,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1714,7 +1720,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1765,7 +1771,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1805,7 +1811,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1830,7 +1836,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1901,7 +1907,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 3 );
 
@@ -1952,7 +1958,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1975,7 +1981,7 @@ describe( 'transform', () => {
 			} );
 
 			it( 'should skip context.aIsStrong and be less important than RemoveOperation', () => {
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2318,7 +2324,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2611,7 +2617,7 @@ describe( 'transform', () => {
 				const anotherRange = Range.createFromParentsAndOffsets( root, 2, root, 2 );
 				const transformBy = new MarkerOperation( 'name', oldRange, anotherRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy, { aIsStrong: true } );
+				const transOp = transform.transform( op, transformBy, contextIsStrong );
 
 				expected.oldRange = anotherRange;
 
diff --git a/tests/model/operation/transform/attribute.js b/tests/model/operation/transform/attribute.js
index 6a5d0f775..3e8610442 100644
--- a/tests/model/operation/transform/attribute.js
+++ b/tests/model/operation/transform/attribute.js
@@ -795,7 +795,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>FooB<$text bold="true">ar</$text></paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #2, then undo', () => {
+			it( 'element into paragraph #2, then undo', () => {
 				john.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
diff --git a/tests/model/operation/transform/insert.js b/tests/model/operation/transform/insert.js
index 635116e14..3eb36286b 100644
--- a/tests/model/operation/transform/insert.js
+++ b/tests/model/operation/transform/insert.js
@@ -811,7 +811,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>Foo</paragraph><paragraph>BarAbc</paragraph>' );
 			} );
 
-			it.skip( 'element, then add marker, split and undo with type #2', () => {
+			it( 'element, then add marker, split and undo with type #2', () => {
 				john.setData( '<paragraph>Foo</paragraph>[]' );
 				kate.setData( '[<paragraph>Foo</paragraph>]' );
 
@@ -845,8 +845,6 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual content:
-				// <paragraph></paragraph><paragraph>Ba</paragraph><paragraph></paragraph>
 				expectClients( '<paragraph>Foo</paragraph><paragraph>BarAbc</paragraph>' );
 			} );
 		} );
diff --git a/tests/model/operation/transform/marker.js b/tests/model/operation/transform/marker.js
index 07b4a2f2b..bb3cf0902 100644
--- a/tests/model/operation/transform/marker.js
+++ b/tests/model/operation/transform/marker.js
@@ -183,7 +183,6 @@ describe( 'transform', () => {
 				kate.remove();
 
 				syncClients();
-
 				expectClients( '<paragraph></paragraph>' );
 
 				john.undo();
@@ -191,8 +190,7 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual result for Kate:
-				// <paragraph><m1:start></m1:start>Fo<m1:end></m1:end><m2:start></m2:start>o<m2:end></m2:end> Bar</paragraph>
+				// Wrong markers transforming.
 				expectClients(
 					'<paragraph>' +
 						'<m1:start></m1:start>Foo<m1:end></m1:end><m2:start></m2:start> Bar<m2:end></m2:end>' +
diff --git a/tests/model/operation/transform/move.js b/tests/model/operation/transform/move.js
index f54108ef8..a7868903b 100644
--- a/tests/model/operation/transform/move.js
+++ b/tests/model/operation/transform/move.js
@@ -335,7 +335,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'text in other user\'s selection', () => {
+			it( 'text in other user\'s selection', () => {
 				john.setData( '<paragraph>[Foo] Bar</paragraph>' );
 				kate.setData( '<paragraph>F[]oo Bar</paragraph>' );
 
@@ -366,7 +366,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'inside moved text', () => {
+			it( 'inside moved text', () => {
 				john.setData( '<paragraph>F[oo Ba]r</paragraph><paragraph>Abc</paragraph>' );
 				kate.setData( '<paragraph>Foo[] Bar</paragraph><paragraph>Abc</paragraph>' );
 
@@ -375,10 +375,6 @@ describe( 'transform', () => {
 
 				syncClients();
 
-				// Actual result for Kate:
-				// <paragraph>F</paragraph><paragraph>r</paragraph><paragraph> BaooAbc</paragraph>
-				// Move operations have wrong targets when they target at same place.
-
 				expectClients(
 					'<paragraph>F</paragraph>' +
 					'<paragraph>r</paragraph>' +
diff --git a/tests/model/operation/transform/remove.js b/tests/model/operation/transform/remove.js
index 92cbc090b..8e2fdcf18 100644
--- a/tests/model/operation/transform/remove.js
+++ b/tests/model/operation/transform/remove.js
@@ -218,7 +218,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element while removing, then undo', () => {
+			it( 'element while removing, then undo', () => {
 				john.setData( '<paragraph>Foo</paragraph><blockQuote>[<paragraph>Bar</paragraph>]</blockQuote>' );
 				kate.setData( '<paragraph>Foo</paragraph><blockQuote>[]<paragraph>Bar</paragraph></blockQuote>' );
 
@@ -226,15 +226,11 @@ describe( 'transform', () => {
 				kate.unwrap();
 
 				syncClients();
-
 				expectClients( '<paragraph>Foo</paragraph>' );
 
 				john.undo();
 
 				syncClients();
-
-				// Actual result:
-				// <paragraph>Foo</paragraph><blockQuote></blockQuote>
 				expectClients(
 					'<paragraph>Foo</paragraph>' +
 					'<paragraph>Bar</paragraph>'
@@ -443,7 +439,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element into paragraph, then undo', () => {
+			it( 'element into paragraph, then undo', () => {
 				john.setData( '<paragraph>F[oo]</paragraph><paragraph>Bar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -451,15 +447,11 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
-
 				expectClients( '<paragraph>FBar</paragraph>' );
 
 				john.undo();
 
 				syncClients();
-
-				// Actual result:
-				// <paragraph>F<paragraph></paragraph>oBar</paragraph>
 				expectClients( '<paragraph>FooBar</paragraph>' );
 			} );
 
diff --git a/tests/model/operation/transform/split.js b/tests/model/operation/transform/split.js
index 7f02b915c..e1b46a707 100644
--- a/tests/model/operation/transform/split.js
+++ b/tests/model/operation/transform/split.js
@@ -90,7 +90,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap', () => {
+			it( 'intersecting wrap', () => {
 				john.setData( '<paragraph>Fo[]o</paragraph>' );
 				kate.setData( '<paragraph>F[oo]</paragraph>' );
 
@@ -98,10 +98,9 @@ describe( 'transform', () => {
 				kate.wrap( 'div' );
 
 				syncClients();
-
 				expectClients(
-					'<paragraph>F</paragraph>' +
-					'<paragraph><div>oo</div></paragraph>'
+					'<paragraph>Fo</paragraph>' +
+					'<paragraph>o</paragraph>'
 				);
 			} );
 		} );
@@ -122,7 +121,7 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'element in same position', () => {
+			it( 'element in same position', () => {
 				john.setData( '<blockQuote><paragraph>[]Foo</paragraph></blockQuote>' );
 				kate.setData( '<blockQuote><paragraph>[]Foo</paragraph></blockQuote>' );
 
@@ -130,7 +129,6 @@ describe( 'transform', () => {
 				kate.unwrap();
 
 				syncClients();
-
 				expectClients( '<blockQuote>Foo</blockQuote>' );
 			} );
 
@@ -285,7 +283,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>FooBar</paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #3', () => {
+			it( 'element into paragraph #3', () => {
 				john.setData( '<paragraph>Foo[]</paragraph><paragraph>Bar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -299,13 +297,10 @@ describe( 'transform', () => {
 				kate.undo();
 
 				syncClients();
-				// Actual content for Kate:
-				// <paragraph>FooBar</paragraph><paragraph></paragraph>
-				// There is a problem in Merge x Split transform in undo case.
 				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph #4', () => {
+			it( 'element into paragraph #4', () => {
 				john.setData( '<paragraph>Foo</paragraph><paragraph>B[]ar</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -313,14 +308,16 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
+				expectClients(
+					'<paragraph>FooB</paragraph>' +
+					'<paragraph>ar</paragraph>'
+				);
 
 				john.undo();
 				kate.undo();
 
-				expectClients(
-					'<paragraph>Fo</paragraph>' +
-					'<paragraph>oBar</paragraph>'
-				);
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 		} );
 
diff --git a/tests/model/operation/transform/unwrap.js b/tests/model/operation/transform/unwrap.js
index 0b14ddd1b..8cba9be85 100644
--- a/tests/model/operation/transform/unwrap.js
+++ b/tests/model/operation/transform/unwrap.js
@@ -50,7 +50,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>Foo</paragraph>' );
 			} );
 
-			it.skip( 'the same element, then undo', () => {
+			it( 'the same element, then undo', () => {
 				john.setData( '<blockQuote>[]<paragraph>Foo</paragraph></blockQuote>' );
 				kate.setData( '<blockQuote>[]<paragraph>Foo</paragraph></blockQuote>' );
 
@@ -63,9 +63,6 @@ describe( 'transform', () => {
 				john.undo();
 
 				syncClients();
-				// Actual content for Kate:
-				// <paragraph><paragraph>Foo</paragraph></paragraph>
-				// Kate has a different order of nodes in graveyard after syncing.
 				expectClients( '<blockQuote><paragraph>Foo</paragraph></blockQuote>' );
 			} );
 		} );
diff --git a/tests/model/operation/transform/utils.js b/tests/model/operation/transform/utils.js
index 8a0557151..016842f9c 100644
--- a/tests/model/operation/transform/utils.js
+++ b/tests/model/operation/transform/utils.js
@@ -253,16 +253,34 @@ function bufferOperations( operations, client ) {
 }
 
 export function syncClients() {
-	for ( const client of clients ) {
-		for ( const item of bufferedOperations ) {
-			const remoteOperations = item.operations.map( op => OperationFactory.fromJSON( JSON.parse( op ), client.document ) );
-			const remoteClient = item.client;
+	const clientsOperations = {};
+
+	// For each client, flatten all buffered operations into one set.
+	for ( const item of bufferedOperations ) {
+		const name = item.client.name;
+
+		if ( !clientsOperations[ name ] ) {
+			clientsOperations[ name ] = [];
+		}
+
+		clientsOperations[ name ].push( ...item.operations );
+	}
 
-			if ( remoteClient == client ) {
+	for ( const localClient of clients ) {
+		for ( const remoteClient of clients ) {
+			if ( remoteClient == localClient ) {
 				continue;
 			}
 
-			const clientOperations = Array.from( client.document.history.getOperations( client.syncedVersion ) );
+			const remoteOperationsJson = clientsOperations[ remoteClient.name ];
+
+			if ( !remoteOperationsJson ) {
+				continue;
+			}
+
+			const remoteOperations = remoteOperationsJson.map( op => OperationFactory.fromJSON( JSON.parse( op ), localClient.document ) );
+
+			const localOperations = Array.from( localClient.document.history.getOperations( localClient.syncedVersion ) );
 
 			let remoteOperationsTransformed = null;
 
@@ -271,21 +289,21 @@ export function syncClients() {
 				padWithNoOps: true
 			};
 
-			if ( client.orderNumber < remoteClient.orderNumber ) {
-				remoteOperationsTransformed = transform.transformSets( clientOperations, remoteOperations, options ).operationsB;
+			if ( localClient.orderNumber < remoteClient.orderNumber ) {
+				remoteOperationsTransformed = transform.transformSets( localOperations, remoteOperations, options ).operationsB;
 			} else {
-				remoteOperationsTransformed = transform.transformSets( remoteOperations, clientOperations, options ).operationsA;
+				remoteOperationsTransformed = transform.transformSets( remoteOperations, localOperations, options ).operationsA;
 			}
 
-			client.editor.model.enqueueChange( 'transparent', writer => {
+			localClient.editor.model.enqueueChange( 'transparent', writer => {
 				for ( const operation of remoteOperationsTransformed ) {
 					writer.batch.addOperation( operation );
-					client.editor.model.applyOperation( operation );
+					localClient.editor.model.applyOperation( operation );
 				}
 			} );
 		}
 
-		client.syncedVersion = client.document.version;
+		localClient.syncedVersion = localClient.document.version;
 	}
 
 	bufferedOperations.clear();
diff --git a/tests/model/operation/transform/wrap.js b/tests/model/operation/transform/wrap.js
index f7e125980..a24e011be 100644
--- a/tests/model/operation/transform/wrap.js
+++ b/tests/model/operation/transform/wrap.js
@@ -63,19 +63,24 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap #2', () => {
-				john.setData( '<paragraph>[Foo]</paragraph>' );
-				kate.setData( '<paragraph>F[o]o</paragraph>' );
+			it( 'intersecting wrap #2', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
+				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
 
-				john.wrap( 'div' );
+				john.wrap( 'blockQuote' );
 				kate.wrap( 'div' );
 
 				syncClients();
-
-				expectClients( '<paragraph><div>Foo</div></pragraph>' );
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+						'<paragraph>Abc</paragraph>' +
+					'</blockQuote>'
+				);
 			} );
 
-			it.skip( 'intersecting wrap, then undo #1', () => {
+			it( 'intersecting wrap, then undo #1', () => {
 				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
 				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
 
@@ -83,12 +88,20 @@ describe( 'transform', () => {
 				kate.wrap( 'div' );
 
 				syncClients();
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+					'</blockQuote>' +
+					'<div>' +
+						'<paragraph>Abc</paragraph>' +
+					'</div>'
+				);
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
-
 				expectClients(
 					'<paragraph>Foo</paragraph>' +
 					'<paragraph>Bar</paragraph>' +
@@ -96,21 +109,30 @@ describe( 'transform', () => {
 				);
 			} );
 
-			it.skip( 'intersecting wrap, then undo #2', () => {
-				john.setData( '<paragraph>[Foo]</paragraph>' );
-				kate.setData( '<paragraph>F[o]o</paragraph>' );
+			it( 'intersecting wrap, then undo #2', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Abc</paragraph>' );
+				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph><paragraph>Abc</paragraph>]' );
 
-				john.wrap( 'div' );
+				john.wrap( 'blockQuote' );
 				kate.wrap( 'div' );
 
 				syncClients();
+				expectClients(
+					'<blockQuote>' +
+						'<paragraph>Foo</paragraph>' +
+						'<paragraph>Bar</paragraph>' +
+					'</blockQuote>' +
+					'<div>' +
+						'<paragraph>Abc</paragraph>' +
+					'</div>'
+				);
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
 
-				expectClients( '<paragraph><div>Foo</div></pragraph>' );
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph><paragraph>Abc</paragraph>' );
 			} );
 
 			it( 'element and text', () => {
@@ -227,14 +249,12 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
-
-				expectClients( '<blockQuote><paragraph>FooBar</paragraph></blockQuote>' );
+				expectClients( '<paragraph>FooBar</paragraph><blockQuote></blockQuote>' );
 
 				john.undo();
 				kate.undo();
 
 				syncClients();
-
 				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 		} );

From f526ee7fd5ae14bf5653d0840e0f3e02225dc34e Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 16:00:45 +0200
Subject: [PATCH 12/26] Changed: `context.getRelation` from function to
 properties.

---
 src/model/operation/transform.js | 38 ++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index c8249cdcf..c93a023f9 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -72,7 +72,7 @@ function updateBaseVersions( operations, baseVersion ) {
 	return operations;
 }
 
-function transform( a, b, context = { aIsStrong: false, wasUndone: () => false, getRelation: () => null } ) {
+function transform( a, b, context = { isStrong: false } ) {
 	const transformationFunction = getTransformation( a, b );
 
 	return transformationFunction( a.clone(), b, context );
@@ -116,13 +116,17 @@ function transformSets( operationsA, operationsB, options ) {
 					const newOpA = transform( opA, opB, {
 						aIsStrong: true,
 						aWasUndone: context.wasUndone( opA ),
-						bWasUndone: context.wasUndone( opB )
+						bWasUndone: context.wasUndone( opB ),
+						abRelation: context.getRelation( opA, opB ),
+						baRelation: context.getRelation( opB, opA )
 					} );
 
 					const newOpB = transform( opB, opA, {
 						aIsStrong: false,
 						aWasUndone: context.wasUndone( opB ),
 						bWasUndone: context.wasUndone( opA ),
+						abRelation: context.getRelation( opB, opA ),
+						baRelation: context.getRelation( opA, opB )
 					} );
 
 					if ( options.useContext ) {
@@ -695,7 +699,7 @@ setTransformation( InsertOperation, InsertOperation, ( a, b, context ) => {
 } );
 
 setTransformation( InsertOperation, MoveOperation, ( a, b, context ) => {
-	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'insertBefore' ) {
+	if ( a.position.isEqual( b.targetPosition ) && context.abRelation == 'insertBefore' ) {
 		return [ a ];
 	}
 
@@ -705,7 +709,7 @@ setTransformation( InsertOperation, MoveOperation, ( a, b, context ) => {
 } );
 
 setTransformation( InsertOperation, SplitOperation, ( a, b, context ) => {
-	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+	if ( a.position.isEqual( b.position ) && context.abRelation == 'insertAtSource' ) {
 		a.position = b.moveTargetPosition;
 
 		return [ a ];
@@ -723,7 +727,7 @@ setTransformation( InsertOperation, MergeOperation, ( a, b ) => {
 } );
 
 setTransformation( InsertOperation, WrapOperation, ( a, b, context ) => {
-	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+	if ( a.position.isEqual( b.position ) && context.abRelation == 'insertInside' ) {
 		a.position = b.targetPosition;
 
 		return [ a ];
@@ -990,7 +994,7 @@ setTransformation( MoveOperation, InsertOperation, ( a, b, context ) => {
 	a.sourcePosition = transformed.start;
 	a.howMany = transformed.end.offset - transformed.start.offset;
 
-	if ( !a.targetPosition.isEqual( b.position ) || context.getRelation( b, a ) == 'insertBefore' ) {
+	if ( !a.targetPosition.isEqual( b.position ) || context.abRelation == 'insertBefore' ) {
 		a.targetPosition = a.targetPosition._getTransformedByInsertOperation( b );
 	}
 
@@ -1007,7 +1011,7 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 
 	// Assign `context.aIsStrong` to a different variable, because the value may change during execution of
 	// this algorithm and we do not want to override original `context.aIsStrong` that will be used in later transformations.
-	let aIsStrong = context.aIsStrong || context.getRelation( a, b ) == 'insertBefore';
+	let aIsStrong = context.aIsStrong || context.abRelation == 'insertBefore';
 
 	// `a.targetPosition` could be affected by the `b` operation. We will transform it.
 	let newTargetPosition;
@@ -1221,7 +1225,7 @@ setTransformation( MoveOperation, SplitOperation, ( a, b, context ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
-	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertAtSource' ) {
+	if ( a.targetPosition.isEqual( b.position ) && context.abRelation == 'insertAtSource' ) {
 		a.targetPosition = b.targetPosition;
 	}
 
@@ -1315,7 +1319,7 @@ setTransformation( MoveOperation, WrapOperation, ( a, b, context ) => {
 	a.howMany = transformed.end.offset - transformed.start.offset;
 	a.targetPosition = newTargetPosition;
 
-	if ( a.targetPosition.isEqual( b.position ) && context.getRelation( a, b ) == 'insertInside' ) {
+	if ( a.targetPosition.isEqual( b.position ) && context.abRelation == 'insertInside' ) {
 		a.targetPosition = b.targetPosition;
 	}
 
@@ -1422,7 +1426,7 @@ setTransformation( RootAttributeOperation, RootAttributeOperation, ( a, b, conte
 // -----------------------
 
 setTransformation( SplitOperation, InsertOperation, ( a, b, context ) => {
-	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertAtSource' ) {
+	if ( a.position.isEqual( b.position ) && context.baRelation == 'insertAtSource' ) {
 		return [ a ];
 	}
 
@@ -1469,7 +1473,7 @@ setTransformation( SplitOperation, MoveOperation, ( a, b, context ) => {
 		return [ a ];
 	}
 
-	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+	if ( a.position.isEqual( b.targetPosition ) && context.abRelation == 'splitBefore' ) {
 		a.position = a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
 
 		return [ a ];
@@ -1491,7 +1495,7 @@ setTransformation( SplitOperation, SplitOperation, ( a, b, context ) => {
 		if ( a.graveyardPosition && b.graveyardPosition && a.graveyardPosition.isEqual( b.graveyardPosition ) ) {
 			return getNoOp();
 		}
-	} else if ( a.position.isEqual( b.insertionPosition ) && context.getRelation( a, b ) == 'splitBefore' ) {
+	} else if ( a.position.isEqual( b.insertionPosition ) && context.abRelation == 'splitBefore' ) {
 		return [ a ];
 	} else {
 		a.position = a.position._getTransformedBySplitOperation( b );
@@ -1522,7 +1526,7 @@ setTransformation( SplitOperation, WrapOperation, ( a, b, context ) => {
 		return [ reversed, a ];
 	}
 
-	if ( a.position.isEqual( b.position ) && context.getRelation( a, b ) == 'splitInside' ) {
+	if ( a.position.isEqual( b.position ) && context.abRelation == 'splitInside' ) {
 		a.position = b.targetPosition;
 	} else {
 		a.position = a.position._getTransformedByWrapOperation( b );
@@ -1538,7 +1542,7 @@ setTransformation( SplitOperation, WrapOperation, ( a, b, context ) => {
 setTransformation( SplitOperation, UnwrapOperation, ( a, b, context ) => {
 	const splitInside = a.position.hasSameParentAs( b.position );
 
-	if ( splitInside && !context.wasUndone( b ) ) {
+	if ( splitInside && !context.bWasUndone ) {
 		const path = b.graveyardPosition.path.slice();
 		path.push( 0 );
 
@@ -1557,7 +1561,7 @@ setTransformation( SplitOperation, UnwrapOperation, ( a, b, context ) => {
 // -----------------------
 
 setTransformation( WrapOperation, InsertOperation, ( a, b, context ) => {
-	if ( a.position.isEqual( b.position ) && context.getRelation( b, a ) == 'insertInside' ) {
+	if ( a.position.isEqual( b.position ) && context.baRelation == 'insertInside' ) {
 		a.howMany += b.howMany;
 
 		return [ a ];
@@ -1589,7 +1593,7 @@ setTransformation( WrapOperation, MoveOperation, ( a, b, context ) => {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMoveOperation( b );
 	}
 
-	if ( a.position.isEqual( b.targetPosition ) && context.getRelation( b, a ) == 'insertInside' ) {
+	if ( a.position.isEqual( b.targetPosition ) && context.baRelation == 'insertInside' ) {
 		a.position._getTransformedByDeletion( b.sourcePosition, b.howMany );
 		a.howMany += b.howMany;
 
@@ -1619,7 +1623,7 @@ setTransformation( WrapOperation, SplitOperation, ( a, b, context ) => {
 	//
 	const isInside = a.position.hasSameParentAs( b.position ) && a.wrappedRange.containsPosition( b.position );
 
-	if ( isInside && context.getRelation( b, a ) !== 'splitInside' ) {
+	if ( isInside && context.baRelation !== 'splitInside' ) {
 		// We cannot just return no-op in this case, because in the mirror case scenario the wrap is reversed, which
 		// might introduce a new node in the graveyard (if the wrap didn't have `graveyardPosition`, then the wrap
 		// created a new element which was put to the graveyard when the wrap was reversed).

From 00c68f2a95a033fa0fb02c705c5a1b8e25b5da28 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Mon, 30 Jul 2018 16:06:27 +0200
Subject: [PATCH 13/26] Changed: Default value for `context.isStrong` is not
 needed.

---
 src/model/operation/transform.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index c93a023f9..1dd415e1a 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -72,7 +72,7 @@ function updateBaseVersions( operations, baseVersion ) {
 	return operations;
 }
 
-function transform( a, b, context = { isStrong: false } ) {
+function transform( a, b, context = {} ) {
 	const transformationFunction = getTransformation( a, b );
 
 	return transformationFunction( a.clone(), b, context );

From 647971b6539a0454d5a88168a9f6d6c73eaf6e3e Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Tue, 31 Jul 2018 12:52:57 +0200
Subject: [PATCH 14/26] Fix: Fixed MergeOperation x SplitOperation algorithm.

---
 src/model/operation/transform.js | 57 ++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 17 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index 1dd415e1a..a4587e4a0 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -113,27 +113,32 @@ function transformSets( operationsA, operationsB, options ) {
 					const opA = opsA[ k ];
 					const opB = opsB[ l ];
 
-					const newOpA = transform( opA, opB, {
+					if ( options.useContext ) {
+						updateRelations( context, opA, opB );
+					}
+
+					const contextAB = {
 						aIsStrong: true,
 						aWasUndone: context.wasUndone( opA ),
 						bWasUndone: context.wasUndone( opB ),
 						abRelation: context.getRelation( opA, opB ),
 						baRelation: context.getRelation( opB, opA )
-					} );
+					};
 
-					const newOpB = transform( opB, opA, {
+					const contextBA = {
 						aIsStrong: false,
 						aWasUndone: context.wasUndone( opB ),
 						bWasUndone: context.wasUndone( opA ),
 						abRelation: context.getRelation( opB, opA ),
 						baRelation: context.getRelation( opA, opB )
-					} );
+					};
+
+					const newOpA = transform( opA, opB, contextAB );
+					const newOpB = transform( opB, opA, contextBA );
 
 					if ( options.useContext ) {
 						updateOriginalOperation( context, opA, newOpA );
 						updateOriginalOperation( context, opB, newOpB );
-
-						updateRelations( context, opA, opB );
 					}
 
 					opsA.splice( k, 1, ...newOpA );
@@ -238,10 +243,15 @@ function updateRelations( context, opA, opB ) {
 					break;
 				}
 
-				case MoveOperation: {
+				case MoveOperation:
+				case RemoveOperation:
+				case ReinsertOperation: {
 					if ( opA.targetPosition.isEqual( opB.sourcePosition ) || opA.targetPosition.isBefore( opB.sourcePosition ) ) {
 						setRelation( context, opA, opB, 'insertBefore' );
 						setRelation( context, opB, opA, 'insertAfter' );
+					} else {
+						setRelation( context, opA, opB, 'insertAfter' );
+						setRelation( context, opB, opA, 'insertBefore' );
 					}
 
 					break;
@@ -272,7 +282,9 @@ function updateRelations( context, opA, opB ) {
 					break;
 				}
 
-				case MoveOperation: {
+				case MoveOperation:
+				case RemoveOperation:
+				case ReinsertOperation: {
 					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
 						setRelation( context, opA, opB, 'splitBefore' );
 						setRelation( context, opB, opA, 'insertAtSource' );
@@ -305,7 +317,9 @@ function updateRelations( context, opA, opB ) {
 					break;
 				}
 
-				case MoveOperation: {
+				case MoveOperation:
+				case RemoveOperation:
+				case ReinsertOperation: {
 					if ( opA.position.isEqual( opB.sourcePosition ) || opA.position.isBefore( opB.sourcePosition ) ) {
 						setRelation( context, opA, opB, 'insertBefore' );
 					}
@@ -897,8 +911,6 @@ setTransformation( MergeOperation, MoveOperation, ( a, b, context ) => {
 } );
 
 setTransformation( MergeOperation, SplitOperation, ( a, b ) => {
-	a.sourcePosition = a.sourcePosition._getTransformedBySplitOperation( b );
-
 	if ( b.graveyardPosition ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByDeletion( b.graveyardPosition, 1 );
 	}
@@ -917,13 +929,18 @@ setTransformation( MergeOperation, SplitOperation, ( a, b ) => {
 	//			This means that `targetPosition` needs to be transformed. This is the default case though.
 	//			For example, if the split would be after `F`, `targetPosition` should also be transformed.
 	//
-	//			There is one exception though - when the split operation is a result of undo. In those cases, it is needed
-	//			to keep `targetPosition` intact, so the nodes are returned to the correct element.
+	//			There is an exception though. It is when merge operation targets into inside of an element.
+	//			Such merge operation can be a result of merge x merge transformation, when merges are identical.
+	//			Such merge operation's source position is in graveyard and we will use that to recognize it
+	//			(although a more precise method would be more correct).
 	//
-	// if ( a.targetPosition.isEqual( b.position ) && b.graveyardPosition ) {
-	// 	return [ a ];
-	// }
+	if ( a.targetPosition.isEqual( b.position ) && a.sourcePosition.root.rootName == '$graveyard' ) {
+		a.sourcePosition = a.sourcePosition._getTransformedBySplitOperation( b );
 
+		return [ a ];
+	}
+
+	a.sourcePosition = a.sourcePosition._getTransformedBySplitOperation( b );
 	a.targetPosition = a.targetPosition._getTransformedBySplitOperation( b );
 
 	return [ a ];
@@ -1011,7 +1028,13 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 
 	// Assign `context.aIsStrong` to a different variable, because the value may change during execution of
 	// this algorithm and we do not want to override original `context.aIsStrong` that will be used in later transformations.
-	let aIsStrong = context.aIsStrong || context.abRelation == 'insertBefore';
+	let aIsStrong = context.aIsStrong;
+
+	if ( context.abRelation == 'insertBefore' ) {
+		aIsStrong = true;
+	} else if ( context.abRelation == 'insertAfter' ) {
+		aIsStrong = false;
+	}
 
 	// `a.targetPosition` could be affected by the `b` operation. We will transform it.
 	let newTargetPosition;

From 252c0778bb1f3d03655482cc58cad03623f8c1ee Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Tue, 31 Jul 2018 13:33:02 +0200
Subject: [PATCH 15/26] Changed: Second parameter of `LiveRange#event:change`
 is now `deletionPosition` not operation that changed the range.

---
 src/model/documentselection.js |  4 +--
 src/model/liverange.js         | 19 +++++++++---
 tests/model/liverange.js       | 57 ++++++++++++++++++++++++----------
 3 files changed, 56 insertions(+), 24 deletions(-)

diff --git a/src/model/documentselection.js b/src/model/documentselection.js
index 3317be489..20d462d8a 100644
--- a/src/model/documentselection.js
+++ b/src/model/documentselection.js
@@ -750,14 +750,14 @@ class LiveSelection extends Selection {
 
 		const liveRange = LiveRange.createFromRange( range );
 
-		liveRange.on( 'change:range', ( evt, oldRange, operation ) => {
+		liveRange.on( 'change:range', ( evt, oldRange, deletionPosition ) => {
 			this._hasChangedRange = true;
 
 			// If `LiveRange` is in whole moved to the graveyard, save necessary data. It will be fixed on `Model#applyOperation` event.
 			if ( liveRange.root == this._document.graveyard ) {
 				this._fixGraveyardRangesData.push( {
 					liveRange,
-					sourcePosition: operation.sourcePosition
+					sourcePosition: deletionPosition
 				} );
 			}
 		} );
diff --git a/src/model/liverange.js b/src/model/liverange.js
index 8ce4b454a..6799bc391 100644
--- a/src/model/liverange.js
+++ b/src/model/liverange.js
@@ -86,9 +86,7 @@ export default class LiveRange extends Range {
 	 * @param {Object} data Object with additional information about the change. Those parameters are passed from
 	 * {@link module:engine/model/document~Document#event:change document change event}.
 	 * @param {String} data.type Change type.
-	 * @param {module:engine/model/batch~Batch} data.batch Batch which changed the live range.
-	 * @param {module:engine/model/range~Range} data.range Range containing the result of applied change.
-	 * @param {module:engine/model/position~Position} data.sourcePosition Source position for move, remove and reinsert change types.
+	 * @param {module:engine/model/position~Position|null} deletionPosition Source position for move, remove and reinsert change types.
 	 */
 
 	/**
@@ -147,16 +145,27 @@ function transform( operation ) {
 	const contentChanged = doesOperationChangeRangeContent( this, operation );
 
 	if ( boundariesChanged ) {
+		let deletionPosition = null;
+
+		if ( result.root.rootName == '$graveyard' ) {
+			if ( operation.type == 'remove' ) {
+				deletionPosition = operation.sourcePosition;
+			} else {
+				// Merge operation.
+				deletionPosition = operation.deletionPosition;
+			}
+		}
+
 		// If range boundaries have changed, fire `change:range` event.
 		const oldRange = Range.createFromRange( this );
 
 		this.start = result.start;
 		this.end = result.end;
 
-		this.fire( 'change:range', oldRange, operation );
+		this.fire( 'change:range', oldRange, deletionPosition );
 	} else if ( contentChanged ) {
 		// If range boundaries have not changed, but there was change inside the range, fire `change:content` event.
-		this.fire( 'change:content', Range.createFromRange( this ), operation );
+		this.fire( 'change:content', Range.createFromRange( this ), null );
 	}
 }
 
diff --git a/tests/model/liverange.js b/tests/model/liverange.js
index 1c3a9ea92..78a56ac7d 100644
--- a/tests/model/liverange.js
+++ b/tests/model/liverange.js
@@ -3,7 +3,6 @@
  * For licensing, see LICENSE.md.
  */
 
-import Batch from '../../src/model/batch';
 import Model from '../../src/model/model';
 import Element from '../../src/model/element';
 import Position from '../../src/model/position';
@@ -90,7 +89,7 @@ describe( 'LiveRange', () => {
 		range.detach();
 	} );
 
-	it( 'should fire change:range event with proper data when its boundaries are changed', () => {
+	it( 'should fire change:range event with when its boundaries are changed', () => {
 		const live = new LiveRange( new Position( root, [ 0, 1, 4 ] ), new Position( root, [ 0, 2, 2 ] ) );
 		const copy = Range.createFromRange( live );
 
@@ -99,15 +98,11 @@ describe( 'LiveRange', () => {
 
 		const sourcePosition = new Position( root, [ 2 ] );
 		const targetPosition = new Position( root, [ 0 ] );
-		const batch = new Batch();
-		let op = null;
 
-		model.enqueueChange( batch, writer => {
+		model.change( writer => {
 			const sourceRange = Range.createFromPositionAndShift( sourcePosition, 1 );
 
 			writer.move( sourceRange, targetPosition );
-
-			op = batch.operations[ 0 ];
 		} );
 
 		expect( spy.calledOnce ).to.be.true;
@@ -115,11 +110,11 @@ describe( 'LiveRange', () => {
 		// First parameter available in event should be a range that is equal to the live range before the live range changed.
 		expect( spy.args[ 0 ][ 1 ].isEqual( copy ) ).to.be.true;
 
-		// Second parameter is the operation that changed the range.
-		expect( spy.args[ 0 ][ 2 ] ).to.equal( op );
+		// Second parameter is null for operations that did not move the range into graveyard.
+		expect( spy.args[ 0 ][ 2 ] ).to.be.null;
 	} );
 
-	it( 'should fire change:content event with proper data when content inside the range has changed', () => {
+	it( 'should fire change:content event when content inside the range has changed', () => {
 		const live = new LiveRange( new Position( root, [ 0, 1 ] ), new Position( root, [ 0, 3 ] ) );
 
 		const spy = sinon.spy();
@@ -127,15 +122,11 @@ describe( 'LiveRange', () => {
 
 		const sourcePosition = new Position( root, [ 0, 2, 0 ] );
 		const targetPosition = new Position( root, [ 0, 4, 0 ] );
-		const batch = new Batch();
-		let op = null;
 
-		model.enqueueChange( batch, writer => {
+		model.change( writer => {
 			const sourceRange = Range.createFromPositionAndShift( sourcePosition, 2 );
 
 			writer.move( sourceRange, targetPosition );
-
-			op = batch.operations[ 0 ];
 		} );
 
 		expect( spy.calledOnce ).to.be.true;
@@ -143,8 +134,40 @@ describe( 'LiveRange', () => {
 		// First parameter available in event should be a range that is equal to the live range before the live range changed.
 		expect( spy.args[ 0 ][ 1 ].isEqual( live ) ).to.be.true;
 
-		// Second parameter is the operation that changed the range.
-		expect( spy.args[ 0 ][ 2 ] ).to.equal( op );
+		// Second parameter is null for operations that did not move the range into graveyard.
+		expect( spy.args[ 0 ][ 2 ] ).to.be.null;
+	} );
+
+	it( 'should pass deletion position if range was removed (remove)', () => {
+		const live = new LiveRange( new Position( root, [ 0, 2 ] ), new Position( root, [ 0, 4 ] ) );
+
+		const spy = sinon.spy();
+		live.on( 'change:range', spy );
+
+		const sourcePosition = new Position( root, [ 0, 0 ] );
+
+		model.change( writer => {
+			writer.remove( Range.createFromPositionAndShift( sourcePosition, 6 ) );
+		} );
+
+		// Second parameter is deletion position.
+		expect( spy.args[ 0 ][ 2 ].isEqual( sourcePosition ) ).to.be.true;
+	} );
+
+	it( 'should pass deletion position if range was removed (merge)', () => {
+		const live = new LiveRange( new Position( root, [ 1 ] ), new Position( root, [ 2 ] ) );
+
+		const spy = sinon.spy();
+		live.on( 'change:range', spy );
+
+		const mergePosition = new Position( root, [ 1 ] );
+
+		model.change( writer => {
+			writer.merge( mergePosition );
+		} );
+
+		// Second parameter is deletion position.
+		expect( spy.args[ 0 ][ 2 ].isEqual( mergePosition ) ).to.be.true;
 	} );
 
 	describe( 'should get transformed and fire change:range if', () => {

From 4637ce454cd026e005858edb50fb5ffaa31ebb3b Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Tue, 31 Jul 2018 16:35:05 +0200
Subject: [PATCH 16/26] Tests: Removed/fixed old transformation tests.

---
 tests/model/operation/transform.js | 54 ++----------------------------
 1 file changed, 2 insertions(+), 52 deletions(-)

diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index d90a85111..ad10c9149 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -682,8 +682,8 @@ describe( 'transform', () => {
 
 				expectOperation( transOp[ 0 ], expected );
 
-				expected.range.start.path = [ 0, 2, 1 ];
-				expected.range.end.path = [ 0, 2, 2 ];
+				expected.range.start.path = [ 0, 2, 3 ];
+				expected.range.end.path = [ 0, 2, 4 ];
 
 				expectOperation( transOp[ 1 ], expected );
 
@@ -693,56 +693,6 @@ describe( 'transform', () => {
 				expectOperation( transOp[ 2 ], expected );
 			} );
 		} );
-
-		describe( 'by RemoveOperation', () => {
-			beforeEach( () => {
-				start = new Position( doc.graveyard, [ 2, 0 ] );
-				end = new Position( doc.graveyard, [ 2, 4 ] );
-
-				range = new Range( start, end );
-
-				op = new AttributeOperation( range, 'foo', 'abc', 'bar', 0 );
-
-				expected.range = new Range( start, end );
-			} );
-
-			it( 'remove operation inserted elements before attribute operation range: increment path', () => {
-				const transformBy = new RemoveOperation(
-					new Position( root, [ 0 ] ),
-					2,
-					new Position( doc.graveyard, [ 0 ] ),
-					0
-				);
-
-				transformBy.targetPosition.path = [ 0 ];
-
-				const transOp = transform.transform( op, transformBy );
-
-				expect( transOp.length ).to.equal( 1 );
-
-				expected.range.start.path = [ 4, 0 ];
-				expected.range.end.path = [ 4, 4 ];
-
-				expectOperation( transOp[ 0 ], expected );
-			} );
-
-			it( 'remove operation inserted elements after attribute operation range: do nothing', () => {
-				const transformBy = new RemoveOperation(
-					new Position( root, [ 0 ] ),
-					2,
-					new Position( doc.graveyard, [ 0 ] ),
-					0
-				);
-
-				transformBy.targetPosition.path = [ 4 ];
-
-				const transOp = transform.transform( op, transformBy );
-
-				expect( transOp.length ).to.equal( 1 );
-
-				expectOperation( transOp[ 0 ], expected );
-			} );
-		} );
 	} );
 
 	describe( 'RootAttributeOperation', () => {

From 975997fd67f0633fbadd9934becc7505a125ced6 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Tue, 31 Jul 2018 16:35:42 +0200
Subject: [PATCH 17/26] Fixed: Improved AttributeOperation and WrapOperation OT
 algorithms.

---
 src/model/operation/transform.js             | 57 ++++++++++----------
 tests/model/operation/transform/attribute.js |  2 +-
 tests/model/operation/transform/remove.js    | 21 +++++++-
 3 files changed, 49 insertions(+), 31 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index a4587e4a0..0462b04f6 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -532,20 +532,10 @@ setTransformation( AttributeOperation, MergeOperation, ( a, b ) => {
 } );
 
 setTransformation( AttributeOperation, MoveOperation, ( a, b ) => {
-	const movedRange = Range.createFromPositionAndShift( b.sourcePosition, b.howMany );
 	const ranges = breakRangeByMoveOperation( a.range, b, true );
 
 	// Create `AttributeOperation`s out of the ranges.
-	return ranges.map( range => {
-		if ( movedRange.containsRange( range, true ) ) {
-			range = range._getTransformedByMoveOperation( b, false )[ 0 ];
-		} else {
-			range = range._getTransformedByDeletion( b.sourcePosition, b.howMany );
-			range = range._getTransformedByInsertion( b.targetPosition, b.howMany, false )[ 0 ];
-		}
-
-		return new AttributeOperation( range, a.key, a.oldValue, a.newValue, a.baseVersion );
-	} );
+	return ranges.map( range => new AttributeOperation( range, a.key, a.oldValue, a.newValue, a.baseVersion ) );
 } );
 
 function breakRangeByMoveOperation( range, moveOp, includeCommon ) {
@@ -553,32 +543,48 @@ function breakRangeByMoveOperation( range, moveOp, includeCommon ) {
 
 	const movedRange = Range.createFromPositionAndShift( moveOp.sourcePosition, moveOp.howMany );
 
-	if ( range.start.hasSameParentAs( moveOp.sourcePosition ) ) {
+	if ( movedRange.containsRange( range, true ) ) {
+		ranges = [ ...range._getTransformedByMoveOperation( moveOp ) ];
+	} else if ( range.start.hasSameParentAs( moveOp.sourcePosition ) ) {
 		ranges = range.getDifference( movedRange );
 
+		_flatMoveTransform( ranges, moveOp );
+
 		if ( includeCommon ) {
 			const common = range.getIntersection( movedRange );
 
 			if ( common ) {
-				ranges.push( common );
+				ranges.push( ...common._getTransformedByMoveOperation( moveOp ) );
 			}
 		}
 	} else {
 		ranges = [ range ];
+
+		_flatMoveTransform( ranges, moveOp );
 	}
 
+	return ranges;
+}
+
+function _flatMoveTransform( ranges, moveOp ) {
+	const targetPosition = moveOp.getMovedRangeStart();
+
 	for ( let i = 0; i < ranges.length; i++ ) {
-		const range = ranges[ i ];
+		let range = ranges[ i ];
 
-		if ( range.start.hasSameParentAs( moveOp.targetPosition ) && range.containsPosition( moveOp.targetPosition ) ) {
-			ranges.splice( i, 1,
-				new Range( range.start, moveOp.targetPosition ),
-				new Range( moveOp.targetPosition, range.end )
-			);
+		if ( range.start.hasSameParentAs( moveOp.sourcePosition ) ) {
+			range = range._getTransformedByDeletion( moveOp.sourcePosition, moveOp.howMany );
 		}
-	}
 
-	return ranges;
+		if ( range.start.hasSameParentAs( targetPosition ) ) {
+			const result = range._getTransformedByInsertion( targetPosition, moveOp.howMany, true );
+
+			ranges.splice( i, 1, ...result );
+			i = i - 1 + result.length;
+		} else {
+			ranges[ i ] = range;
+		}
+	}
 }
 
 setTransformation( AttributeOperation, SplitOperation, ( a, b ) => {
@@ -1625,12 +1631,6 @@ setTransformation( WrapOperation, MoveOperation, ( a, b, context ) => {
 
 	const ranges = breakRangeByMoveOperation( a.wrappedRange, b, false );
 
-	if ( ranges.length == 0 ) {
-		const range = a.wrappedRange._getTransformedByMoveOperation( b )[ 0 ];
-
-		ranges.push( range );
-	}
-
 	return ranges.reverse().map( range => {
 		const howMany = range.end.offset - range.start.offset;
 		const elementOrGraveyardPosition = a.graveyardPosition ? a.graveyardPosition : a.element;
@@ -1640,7 +1640,7 @@ setTransformation( WrapOperation, MoveOperation, ( a, b, context ) => {
 } );
 
 setTransformation( WrapOperation, SplitOperation, ( a, b, context ) => {
-	// Case 1:	If range to wrap got split by split operation cancel the wrapping.
+	// Case 1:	If range to wrap got split cancel the wrapping.
 	//			Do that only if this is not undo mode. If `b` operation was earlier transformed by unwrap operation
 	//			and the split position was inside the unwrapped range, then proceed without special case.
 	//
@@ -1652,6 +1652,7 @@ setTransformation( WrapOperation, SplitOperation, ( a, b, context ) => {
 		// created a new element which was put to the graveyard when the wrap was reversed).
 		//
 		// Instead, a node in graveyard will be inserted.
+		//
 		if ( a.element ) {
 			const graveyard = a.position.root.document.graveyard;
 			const graveyardPosition = new Position( graveyard, [ 0 ] );
diff --git a/tests/model/operation/transform/attribute.js b/tests/model/operation/transform/attribute.js
index 3e8610442..f67e237e1 100644
--- a/tests/model/operation/transform/attribute.js
+++ b/tests/model/operation/transform/attribute.js
@@ -325,7 +325,7 @@ describe( 'transform', () => {
 				kate.setData( '<paragraph>F[oo] Bar</paragraph>' );
 
 				john.setAttribute( 'bold', true );
-				kate.move( [ 0, 7 ], [ 0, 1 ], [ 0, 3 ] );
+				kate.move( [ 0, 7 ] );
 
 				syncClients();
 
diff --git a/tests/model/operation/transform/remove.js b/tests/model/operation/transform/remove.js
index 8e2fdcf18..75635562f 100644
--- a/tests/model/operation/transform/remove.js
+++ b/tests/model/operation/transform/remove.js
@@ -158,13 +158,30 @@ describe( 'transform', () => {
 				kate.wrap( 'blockQuote' );
 
 				syncClients();
+				expectClients( '<paragraph>Foo</paragraph>' );
+
+				john.undo();
+
+				syncClients();
+
+				expectClients(
+					'<paragraph>Foo</paragraph>' +
+					'<blockQuote>' +
+						'<paragraph>Bar</paragraph>' +
+					'</blockQuote>'
+				);
+			} );
 
+			it( 'element while removing, then undo #2', () => {
+				john.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]' );
+				kate.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]' );
+
+				john.remove();
 				john.undo();
+				kate.wrap( 'blockQuote' );
 
 				syncClients();
 
-				// Actual content:
-				// <paragraph>Foo</paragraph><paragraph>Bar</paragraph><blockQuote></blockQuote>
 				expectClients(
 					'<paragraph>Foo</paragraph>' +
 					'<blockQuote>' +

From 4cf77847d7a7fd967c64f99fd5e422273016c8d6 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Wed, 1 Aug 2018 12:59:51 +0200
Subject: [PATCH 18/26] Fixed: `SplitOperation` and `WrapOperation`
 `graveyardPosition` should stick to the node they "represent".

---
 src/model/operation/splitoperation.js | 4 ++++
 src/model/operation/wrapoperation.js  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/src/model/operation/splitoperation.js b/src/model/operation/splitoperation.js
index 0b00419d5..4ed0267c1 100644
--- a/src/model/operation/splitoperation.js
+++ b/src/model/operation/splitoperation.js
@@ -43,6 +43,10 @@ export default class SplitOperation extends Operation {
 		this.position.stickiness = 'toNext';
 
 		this.graveyardPosition = graveyardPosition ? Position.createFromPosition( graveyardPosition ) : null;
+
+		if ( this.graveyardPosition ) {
+			this.graveyardPosition.stickiness = 'toNext';
+		}
 	}
 
 	/**
diff --git a/src/model/operation/wrapoperation.js b/src/model/operation/wrapoperation.js
index 5de2c6a68..4b502bd35 100644
--- a/src/model/operation/wrapoperation.js
+++ b/src/model/operation/wrapoperation.js
@@ -62,6 +62,10 @@ export default class WrapOperation extends Operation {
 		this.element = elementOrPosition instanceof Element ? elementOrPosition : null;
 
 		this.graveyardPosition = elementOrPosition instanceof Element ? null : Position.createFromPosition( elementOrPosition );
+
+		if ( this.graveyardPosition ) {
+			this.graveyardPosition.stickiness = 'toNext';
+		}
 	}
 
 	/**

From 69a90da0cd7998cc50b44c7e9ac1aa3cb6650005 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Wed, 1 Aug 2018 13:00:57 +0200
Subject: [PATCH 19/26] Fixed: Range#_getTransformedByUnwrapOperation if the
 operation is a special case of unwrapping a node that is already in the
 graveyard.

---
 src/model/position.js | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/model/position.js b/src/model/position.js
index 4a91b11f9..a990b0b9b 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -599,15 +599,17 @@ export default class Position {
 			unwrappedRange.start.isEqual( this ) ||
 			unwrappedRange.end.isEqual( this );
 
+		let pos;
+
 		if ( isContained ) {
-			return this._getCombined( operation.position, operation.targetPosition );
+			pos = this._getCombined( operation.position, operation.targetPosition );
 		} else if ( this.isEqual( operation.targetPosition ) ) {
 			return Position.createFromPosition( this );
 		} else {
-			const pos = this._getTransformedByInsertion( operation.targetPosition, operation.howMany - 1 );
-
-			return pos._getTransformedByInsertion( operation.graveyardPosition, 1 );
+			pos = this._getTransformedByInsertion( operation.targetPosition, operation.howMany );
 		}
+
+		return pos._getTransformedByMove( operation.targetPosition.getShiftedBy( operation.howMany ), operation.graveyardPosition, 1 );
 	}
 
 	/**

From 20723dcd3043146faf89d90d3414c58870041a89 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Wed, 1 Aug 2018 13:02:18 +0200
Subject: [PATCH 20/26] Fixed: WrapOperation x MergeOperation will not create
 empty wrappings anymore.

---
 src/model/operation/transform.js        | 51 +++++++++++++++++++------
 tests/model/operation/transform/wrap.js |  4 +-
 2 files changed, 41 insertions(+), 14 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index 0462b04f6..5cee039b6 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -970,6 +970,23 @@ setTransformation( MergeOperation, WrapOperation, ( a, b ) => {
 		return [ a ];
 	}
 
+	// Case 2:	Merged element is wrapped and this is the last (only) element in the wrap.
+	//			Because of how this is resolved in `WrapOperation` x `MergeOperation`, we need to apply special handling here.
+	//			If the last element from wrapped range is "removed" from it, the wrap is effectively on empty range.
+	//			In that case, the wrapper element is moved to graveyard. This happens in `WrapOperation` x
+	//			`MergeOperation` and we need to mirror it here.
+	//
+	if ( b.position.isEqual( a.deletionPosition ) && b.howMany == 1 ) {
+		// We need to change `MergeOperation#graveyardPosition` so the merged node is moved into the wrapper element.
+		// Since `UnwrapOperation` created from reverse has graveyard position at [ 0 ], we can safely set the path here to [ 0, 0 ].
+		a.graveyardPosition = new Position( a.graveyardPosition.root, [ 0, 0 ] );
+
+		return [
+			b.getReversed(),
+			a
+		];
+	}
+
 	a.sourcePosition = a.sourcePosition._getTransformedByWrapOperation( b );
 	a.targetPosition = a.targetPosition._getTransformedByWrapOperation( b );
 
@@ -1561,8 +1578,8 @@ setTransformation( SplitOperation, WrapOperation, ( a, b, context ) => {
 		a.position = a.position._getTransformedByWrapOperation( b );
 	}
 
-	if ( a.graveyardPosition && b.graveyardPosition ) {
-		a.graveyardPosition = a.graveyardPosition._getTransformedByDeletion( b.graveyardPosition, 1 );
+	if ( a.graveyardPosition ) {
+		a.graveyardPosition = a.graveyardPosition._getTransformedByWrapOperation( b );
 	}
 
 	return [ a ];
@@ -1581,7 +1598,7 @@ setTransformation( SplitOperation, UnwrapOperation, ( a, b, context ) => {
 	}
 
 	if ( a.graveyardPosition ) {
-		a.graveyardPosition = a.graveyardPosition._getTransformedByInsertion( b.graveyardPosition, 1 );
+		a.graveyardPosition = a.graveyardPosition._getTransformedByUnwrapOperation( b );
 	}
 
 	return [ a ];
@@ -1865,11 +1882,21 @@ setTransformation( UnwrapOperation, MergeOperation, ( a, b, context ) => {
 		return [ b.getReversed(), a ];
 	}
 
-	const transformed = a.unwrappedRange._getTransformedByMergeOperation( b );
+	// // Case 2:	The element to unwrap was merged-to and has new nodes.
+	// //
+	// if ( a.position.hasSameParentAs( b.targetPosition ) ) {
+	// 	// Merge operation needs `howMany`!
+	// }
 
-	a.position = transformed.start;
-	a.position.stickiness = 'toPrevious';
-	a.howMany = transformed.end.offset - transformed.start.offset;
+	if ( a.position.hasSameParentAs( b.graveyardPosition ) ) {
+		a.howMany++;
+	}
+
+	if ( a.position.hasSameParentAs( b.deletionPosition ) ) {
+		a.howMany--;
+	}
+
+	a.position = a.position._getTransformedByMergeOperation( b );
 
 	if ( !a.graveyardPosition.isEqual( b.graveyardPosition ) || !context.aIsStrong ) {
 		a.graveyardPosition = a.graveyardPosition._getTransformedByMergeOperation( b );
@@ -1923,17 +1950,17 @@ setTransformation( UnwrapOperation, SplitOperation, ( a, b ) => {
 	// Case 2:	The split element is the last element in unwrapped element. In this case, we need to manually modify
 	//			`howMany` property because it wouldn't be correctly calculated by `_getTransformedBySplitOperation`.
 	//
-	if ( b.insertionPosition.isEqual( a.position.getShiftedBy( a.howMany ) ) ) {
+	if ( a.position.hasSameParentAs( b.insertionPosition ) ) {
 		a.howMany++;
 
 		return [ a ];
 	}
 
-	const transformed = a.unwrappedRange._getTransformedBySplitOperation( b );
+	a.position = a.position._getTransformedBySplitOperation( b );
 
-	a.position = transformed.start;
-	a.position.stickiness = 'toPrevious';
-	a.howMany = transformed.end.offset - transformed.start.offset;
+	if ( b.graveyardPosition && b.graveyardPosition.hasSameParentAs( a.position ) ) {
+		a.howMany--;
+	}
 
 	a.graveyardPosition = a.graveyardPosition._getTransformedBySplitOperation( b );
 
diff --git a/tests/model/operation/transform/wrap.js b/tests/model/operation/transform/wrap.js
index a24e011be..2e53adde2 100644
--- a/tests/model/operation/transform/wrap.js
+++ b/tests/model/operation/transform/wrap.js
@@ -241,7 +241,7 @@ describe( 'transform', () => {
 				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
 			} );
 
-			it.skip( 'element into paragraph, then undo', () => {
+			it( 'element into paragraph, then undo', () => {
 				john.setData( '<paragraph>Foo</paragraph>[<paragraph>Bar</paragraph>]' );
 				kate.setData( '<paragraph>Foo</paragraph>[]<paragraph>Bar</paragraph>' );
 
@@ -249,7 +249,7 @@ describe( 'transform', () => {
 				kate.merge();
 
 				syncClients();
-				expectClients( '<paragraph>FooBar</paragraph><blockQuote></blockQuote>' );
+				expectClients( '<paragraph>FooBar</paragraph>' );
 
 				john.undo();
 				kate.undo();

From d7b475cb2ddc747068762f5abb0eebbfd052593d Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Wed, 1 Aug 2018 15:09:27 +0200
Subject: [PATCH 21/26] Fixed: Preventing "empty" wraps also in MoveOperation x
 WrapOperation cases.

---
 src/model/position.js                   | 11 ++-
 tests/model/operation/transform/wrap.js | 96 +++++++++++++++++++++++++
 2 files changed, 105 insertions(+), 2 deletions(-)

diff --git a/src/model/position.js b/src/model/position.js
index a990b0b9b..8973e214b 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -604,12 +604,19 @@ export default class Position {
 		if ( isContained ) {
 			pos = this._getCombined( operation.position, operation.targetPosition );
 		} else if ( this.isEqual( operation.targetPosition ) ) {
-			return Position.createFromPosition( this );
+			pos = Position.createFromPosition( this );
 		} else {
 			pos = this._getTransformedByInsertion( operation.targetPosition, operation.howMany );
 		}
 
-		return pos._getTransformedByMove( operation.targetPosition.getShiftedBy( operation.howMany ), operation.graveyardPosition, 1 );
+		const targetPosition = operation.targetPosition.getShiftedBy( operation.howMany );
+
+		if ( !targetPosition.isEqual( operation.graveyardPosition ) ) {
+			pos = pos._getTransformedByDeletion( targetPosition, 1 );
+			pos = pos._getTransformedByInsertion( operation.graveyardPosition, 1 );
+		}
+
+		return pos;
 	}
 
 	/**
diff --git a/tests/model/operation/transform/wrap.js b/tests/model/operation/transform/wrap.js
index 2e53adde2..e03efc0e5 100644
--- a/tests/model/operation/transform/wrap.js
+++ b/tests/model/operation/transform/wrap.js
@@ -211,6 +211,102 @@ describe( 'transform', () => {
 			} );
 		} );
 
+		describe( 'by remove', () => {
+			it( 'remove the only wrapped element', () => {
+				john.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+				kate.remove();
+
+				syncClients();
+
+				expectClients( '<paragraph>Bar</paragraph>' );
+			} );
+
+			it( 'remove one of two wrapped elements', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+				kate.remove();
+
+				syncClients();
+
+				expectClients( '<blockQuote><paragraph>Bar</paragraph></blockQuote>' );
+			} );
+
+			it( 'remove all wrapped elements', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Xyz</paragraph>' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph><paragraph>Xyz</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+
+				kate.remove();
+				kate.setSelection( [ 0 ], [ 1 ] );
+				kate.remove();
+
+				syncClients();
+
+				expectClients( '<paragraph>Xyz</paragraph>' );
+			} );
+
+			it( 'remove the only wrapped element with undo', () => {
+				john.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+				kate.remove();
+
+				syncClients();
+				expectClients( '<paragraph>Bar</paragraph>' );
+
+				john.undo();
+				kate.undo();
+
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
+			} );
+
+			it( 'remove one of two wrapped elements with undo', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+				kate.remove();
+
+				syncClients();
+				expectClients( '<blockQuote><paragraph>Bar</paragraph></blockQuote>' );
+
+				john.undo();
+				kate.undo();
+
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph>' );
+			} );
+
+			it( 'remove all wrapped elements with undo', () => {
+				john.setData( '[<paragraph>Foo</paragraph><paragraph>Bar</paragraph>]<paragraph>Xyz</paragraph>' );
+				kate.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph><paragraph>Xyz</paragraph>' );
+
+				john.wrap( 'blockQuote' );
+
+				kate.remove();
+				kate.setSelection( [ 0 ], [ 1 ] );
+				kate.remove();
+
+				syncClients();
+				expectClients( '<paragraph>Xyz</paragraph>' );
+
+				john.undo();
+				kate.undo();
+				kate.undo();
+
+				syncClients();
+				expectClients( '<paragraph>Foo</paragraph><paragraph>Bar</paragraph><paragraph>Xyz</paragraph>' );
+			} );
+		} );
+
 		describe( 'by merge', () => {
 			it( 'element into paragraph #1', () => {
 				john.setData( '[<paragraph>Foo</paragraph>]<paragraph>Bar</paragraph>' );

From fd2f4f539750c527417457df0e9eb02d729e1db2 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Wed, 1 Aug 2018 17:02:51 +0200
Subject: [PATCH 22/26] Fix: Final OT followup fixes after merging several
 branches.

---
 src/model/operation/transform.js   | 46 ++++++++++++++++++++----------
 tests/model/liverange.js           | 34 ++++++++++++++++++----
 tests/model/operation/transform.js | 10 ++++++-
 3 files changed, 69 insertions(+), 21 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index 1d6a8f156..b1cd0724b 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -60,10 +60,10 @@ function transform( a, b, context = {} ) {
 		log.error( 'Transformed operation', a );
 		log.error( 'Operation transformed by', b );
 		log.error( 'context.aIsStrong', context.aIsStrong );
-		log.error( 'context.wasUndone( a )', context.wasUndone( a ) );
-		log.error( 'context.wasUndone( b )', context.wasUndone( b ) );
-		log.error( 'context.getRelation( a, b )', context.getRelation( a, b ) );
-		log.error( 'context.getRelation( b, a )', context.getRelation( b, a ) );
+		log.error( 'context.aWasUndone', context.aWasUndone );
+		log.error( 'context.bWasUndone', context.bWasUndone );
+		log.error( 'context.abRelation', context.abRelation );
+		log.error( 'context.baRelation', context.baRelation );
 
 		throw e;
 	}
@@ -500,15 +500,18 @@ setTransformation( AttributeOperation, MergeOperation, ( a, b ) => {
 	//			Do it only, if there is more than one element in attribute range. If there is only one element,
 	//			it will be handled by the default algorithm.
 	//
-	const howMany = a.range.end.offset - a.range.start.offset;
-
-	if ( howMany > 1 && a.range.start.hasSameParentAs( b.deletionPosition ) ) {
+	if ( a.range.start.hasSameParentAs( b.deletionPosition ) ) {
 		if ( a.range.containsPosition( b.deletionPosition ) || a.range.start.isEqual( b.deletionPosition ) ) {
 			ranges.push( Range.createFromPositionAndShift( b.graveyardPosition, 1 ) );
 		}
 	}
 
-	ranges.push( a.range._getTransformedByMergeOperation( b ) );
+	const range = a.range._getTransformedByMergeOperation( b );
+
+	// Do not add empty (collapsed) ranges to the result. `range` may be collapsed if it contained only the merged element.
+	if ( !range.isCollapsed ) {
+		ranges.push( range );
+	}
 
 	// Create `AttributeOperation`s out of the ranges.
 	return ranges.map( range => {
@@ -605,10 +608,13 @@ setTransformation( AttributeOperation, SplitOperation, ( a, b ) => {
 	if ( a.range.start.hasSameParentAs( b.position ) && a.range.containsPosition( b.position ) ) {
 		const secondPart = a.clone();
 
-		secondPart.range.start = Position.createFromPosition( b.moveTargetPosition );
-		secondPart.range.end = a.range.end._getCombined( b.position, b.moveTargetPosition );
+		secondPart.range = new Range(
+			Position.createFromPosition( b.moveTargetPosition ),
+			a.range.end._getCombined( b.position, b.moveTargetPosition )
+		);
 
 		a.range.end = Position.createFromPosition( b.position );
+		a.range.end.stickiness = 'toPrevious';
 
 		return [ a, secondPart ];
 	}
@@ -1036,7 +1042,7 @@ setTransformation( MoveOperation, MoveOperation, ( a, b, context ) => {
 
 	// Assign `context.aIsStrong` to a different variable, because the value may change during execution of
 	// this algorithm and we do not want to override original `context.aIsStrong` that will be used in later transformations.
-	let aIsStrong = context.aIsStrong || context.getRelation( a, b ) == 'insertBefore';
+	let aIsStrong = context.aIsStrong;
 
 	if ( context.abRelation == 'insertBefore' ) {
 		aIsStrong = true;
@@ -1379,6 +1385,7 @@ setTransformation( RenameOperation, InsertOperation, ( a, b ) => {
 setTransformation( RenameOperation, MergeOperation, ( a, b ) => {
 	if ( a.position.isEqual( b.deletionPosition ) ) {
 		a.position = Position.createFromPosition( b.graveyardPosition );
+		a.position.stickiness = 'toNext';
 
 		return [ a ];
 	}
@@ -1613,15 +1620,24 @@ setTransformation( WrapOperation, InsertOperation, ( a, b, context ) => {
 } );
 
 setTransformation( WrapOperation, MergeOperation, ( a, b ) => {
+	if ( a.graveyardPosition ) {
+		a.graveyardPosition = a.graveyardPosition._getTransformedByInsertion( b.graveyardPosition, 1 );
+	}
+
+	// Case 1:	The element to wrap got merged.
+	//
+	if ( a.position.isEqual( b.deletionPosition ) ) {
+		a.position = Position.createFromPosition( b.graveyardPosition );
+		a.position.stickiness = 'toNext';
+
+		return [ a ];
+	}
+
 	const transformed = a.wrappedRange._getTransformedByMergeOperation( b );
 
 	a.position = transformed.start;
 	a.howMany = transformed.end.offset - transformed.start.offset;
 
-	if ( a.graveyardPosition ) {
-		a.graveyardPosition = a.graveyardPosition._getTransformedByInsertion( b.graveyardPosition, 1 );
-	}
-
 	return [ a ];
 } );
 
diff --git a/tests/model/liverange.js b/tests/model/liverange.js
index 78a56ac7d..ed005f2b1 100644
--- a/tests/model/liverange.js
+++ b/tests/model/liverange.js
@@ -9,6 +9,8 @@ import Position from '../../src/model/position';
 import LiveRange from '../../src/model/liverange';
 import Range from '../../src/model/range';
 import Text from '../../src/model/text';
+import MoveOperation from '../../src/model/operation/moveoperation';
+import MergeOperation from '../../src/model/operation/mergeoperation';
 import { stringify, setData } from '../../src/dev-utils/model';
 
 describe( 'LiveRange', () => {
@@ -154,20 +156,42 @@ describe( 'LiveRange', () => {
 		expect( spy.args[ 0 ][ 2 ].isEqual( sourcePosition ) ).to.be.true;
 	} );
 
+	// This scenario is hypothetically possible during OT if the element to merge-into was removed.
+	// In that case a live range inside the merged element will be merged into an element which is in graveyard.
+	// Because it may happen only in OT, in the test below we will generate operations by hand.
 	it( 'should pass deletion position if range was removed (merge)', () => {
-		const live = new LiveRange( new Position( root, [ 1 ] ), new Position( root, [ 2 ] ) );
+		const live = new LiveRange( new Position( root, [ 1, 0 ] ), new Position( root, [ 1, 1 ] ) );
 
 		const spy = sinon.spy();
 		live.on( 'change:range', spy );
 
-		const mergePosition = new Position( root, [ 1 ] );
-
 		model.change( writer => {
-			writer.merge( mergePosition );
+			const batch = writer.batch;
+			const gy = model.document.graveyard;
+
+			const remove = new MoveOperation(
+				new Position( root, [ 0 ] ),
+				1,
+				new Position( gy, [ 0 ] ),
+				model.document.version
+			);
+
+			const merge = new MergeOperation(
+				new Position( root, [ 0, 0 ] ),
+				new Position( gy, [ 0, 0 ] ),
+				new Position( gy, [ 0 ] ),
+				model.document.version + 1
+			);
+
+			batch.addOperation( remove );
+			model.applyOperation( remove );
+
+			batch.addOperation( merge );
+			model.applyOperation( merge );
 		} );
 
 		// Second parameter is deletion position.
-		expect( spy.args[ 0 ][ 2 ].isEqual( mergePosition ) ).to.be.true;
+		expect( spy.args[ 1 ][ 2 ].isEqual( new Position( root, [ 0 ] ) ) ).to.be.true;
 	} );
 
 	describe( 'should get transformed and fire change:range if', () => {
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index 490ca2c1a..132df0102 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -73,10 +73,18 @@ describe( 'transform', () => {
 		a.position = null;
 
 		expect( () => {
-			transform.transform( a, b );
+			transform.transform( a, b, {
+				aIsStrong: true,
+				aWasUndone: false,
+				bWasUndone: false,
+				abRelation: null,
+				baRelation: null
+			} );
 		} ).to.throw();
 
 		sinon.assert.called( spy );
+
+		log.error.restore();
 	} );
 
 	describe( 'InsertOperation', () => {

From 62a3cc20fab3f08b5522114df8db6ceb7971373c Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Thu, 9 Aug 2018 13:19:07 +0200
Subject: [PATCH 23/26] Change: Make second parameter of
 `LiveRange#event:change` an object.

---
 src/model/documentselection.js | 4 ++--
 src/model/liverange.js         | 7 +++----
 tests/model/liverange.js       | 8 ++++----
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/model/documentselection.js b/src/model/documentselection.js
index 20d462d8a..853c1b748 100644
--- a/src/model/documentselection.js
+++ b/src/model/documentselection.js
@@ -750,14 +750,14 @@ class LiveSelection extends Selection {
 
 		const liveRange = LiveRange.createFromRange( range );
 
-		liveRange.on( 'change:range', ( evt, oldRange, deletionPosition ) => {
+		liveRange.on( 'change:range', ( evt, oldRange, data ) => {
 			this._hasChangedRange = true;
 
 			// If `LiveRange` is in whole moved to the graveyard, save necessary data. It will be fixed on `Model#applyOperation` event.
 			if ( liveRange.root == this._document.graveyard ) {
 				this._fixGraveyardRangesData.push( {
 					liveRange,
-					sourcePosition: deletionPosition
+					sourcePosition: data.deletionPosition
 				} );
 			}
 		} );
diff --git a/src/model/liverange.js b/src/model/liverange.js
index 6799bc391..73480f7b8 100644
--- a/src/model/liverange.js
+++ b/src/model/liverange.js
@@ -143,10 +143,9 @@ function transform( operation ) {
 	const result = Range.createFromRanges( ranges );
 	const boundariesChanged = !result.isEqual( this );
 	const contentChanged = doesOperationChangeRangeContent( this, operation );
+	let deletionPosition = null;
 
 	if ( boundariesChanged ) {
-		let deletionPosition = null;
-
 		if ( result.root.rootName == '$graveyard' ) {
 			if ( operation.type == 'remove' ) {
 				deletionPosition = operation.sourcePosition;
@@ -162,10 +161,10 @@ function transform( operation ) {
 		this.start = result.start;
 		this.end = result.end;
 
-		this.fire( 'change:range', oldRange, deletionPosition );
+		this.fire( 'change:range', oldRange, { deletionPosition } );
 	} else if ( contentChanged ) {
 		// If range boundaries have not changed, but there was change inside the range, fire `change:content` event.
-		this.fire( 'change:content', Range.createFromRange( this ), null );
+		this.fire( 'change:content', Range.createFromRange( this ), { deletionPosition } );
 	}
 }
 
diff --git a/tests/model/liverange.js b/tests/model/liverange.js
index ed005f2b1..dd74cf780 100644
--- a/tests/model/liverange.js
+++ b/tests/model/liverange.js
@@ -113,7 +113,7 @@ describe( 'LiveRange', () => {
 		expect( spy.args[ 0 ][ 1 ].isEqual( copy ) ).to.be.true;
 
 		// Second parameter is null for operations that did not move the range into graveyard.
-		expect( spy.args[ 0 ][ 2 ] ).to.be.null;
+		expect( spy.args[ 0 ][ 2 ].deletionPosition ).to.be.null;
 	} );
 
 	it( 'should fire change:content event when content inside the range has changed', () => {
@@ -137,7 +137,7 @@ describe( 'LiveRange', () => {
 		expect( spy.args[ 0 ][ 1 ].isEqual( live ) ).to.be.true;
 
 		// Second parameter is null for operations that did not move the range into graveyard.
-		expect( spy.args[ 0 ][ 2 ] ).to.be.null;
+		expect( spy.args[ 0 ][ 2 ].deletionPosition ).to.be.null;
 	} );
 
 	it( 'should pass deletion position if range was removed (remove)', () => {
@@ -153,7 +153,7 @@ describe( 'LiveRange', () => {
 		} );
 
 		// Second parameter is deletion position.
-		expect( spy.args[ 0 ][ 2 ].isEqual( sourcePosition ) ).to.be.true;
+		expect( spy.args[ 0 ][ 2 ].deletionPosition.isEqual( sourcePosition ) ).to.be.true;
 	} );
 
 	// This scenario is hypothetically possible during OT if the element to merge-into was removed.
@@ -191,7 +191,7 @@ describe( 'LiveRange', () => {
 		} );
 
 		// Second parameter is deletion position.
-		expect( spy.args[ 1 ][ 2 ].isEqual( new Position( root, [ 0 ] ) ) ).to.be.true;
+		expect( spy.args[ 1 ][ 2 ].deletionPosition.isEqual( new Position( root, [ 0 ] ) ) ).to.be.true;
 	} );
 
 	describe( 'should get transformed and fire change:range if', () => {

From a2b3803ed41ac9d4f95079c88011f8aebeeff645 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Thu, 9 Aug 2018 13:19:34 +0200
Subject: [PATCH 24/26] Change: Export functions in operation/transform.js as
 separate functions, not an object.

---
 src/model/operation/transform.js         |   9 +-
 tests/model/operation/transform.js       | 302 +++++++++++------------
 tests/model/operation/transform/utils.js |   6 +-
 3 files changed, 156 insertions(+), 161 deletions(-)

diff --git a/src/model/operation/transform.js b/src/model/operation/transform.js
index b1cd0724b..bca951da0 100644
--- a/src/model/operation/transform.js
+++ b/src/model/operation/transform.js
@@ -50,7 +50,7 @@ function updateBaseVersions( operations, baseVersion ) {
 	return operations;
 }
 
-function transform( a, b, context = {} ) {
+export function transform( a, b, context = {} ) {
 	const transformationFunction = getTransformation( a, b );
 
 	try {
@@ -69,7 +69,7 @@ function transform( a, b, context = {} ) {
 	}
 }
 
-function transformSets( operationsA, operationsB, options ) {
+export function transformSets( operationsA, operationsB, options ) {
 	operationsA = operationsA.slice();
 	operationsB = operationsB.slice();
 
@@ -163,11 +163,6 @@ function transformSets( operationsA, operationsB, options ) {
 	return { operationsA, operationsB };
 }
 
-export default {
-	transform,
-	transformSets
-};
-
 function padWithNoOps( operations, howMany ) {
 	for ( let i = 0; i < howMany; i++ ) {
 		operations.push( new NoOperation( 0 ) );
diff --git a/tests/model/operation/transform.js b/tests/model/operation/transform.js
index 132df0102..f7903230c 100644
--- a/tests/model/operation/transform.js
+++ b/tests/model/operation/transform.js
@@ -3,7 +3,7 @@
  * For licensing, see LICENSE.md.
  */
 
-import transform from '../../../src/model/operation/transform';
+import { transform } from '../../../src/model/operation/transform';
 
 import Model from '../../../src/model/model';
 import RootElement from '../../../src/model/rootelement';
@@ -54,7 +54,7 @@ describe( 'transform', () => {
 		}
 	}
 
-	const contextIsStrong = {
+	const strongContext = {
 		aIsStrong: true
 	};
 
@@ -73,7 +73,7 @@ describe( 'transform', () => {
 		a.position = null;
 
 		expect( () => {
-			transform.transform( a, b, {
+			transform( a, b, {
 				aIsStrong: true,
 				aWasUndone: false,
 				bWasUndone: false,
@@ -112,7 +112,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -125,7 +125,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -139,7 +139,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -153,7 +153,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -166,7 +166,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -180,7 +180,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -193,7 +193,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.path[ 1 ] += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -207,7 +207,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -224,7 +224,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -241,7 +241,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -257,7 +257,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -271,7 +271,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset--;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -286,7 +286,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -300,7 +300,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -315,7 +315,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -329,7 +329,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -344,7 +344,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 				expected.position.offset += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -359,7 +359,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.path[ 1 ] -= 1;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -374,7 +374,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -388,7 +388,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.path[ 1 ] += 2;
 
 				expect( transOp.length ).to.equal( 1 );
@@ -403,7 +403,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -417,7 +417,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.path = [ 1, 2, 2 ];
 
 				expect( transOp.length ).to.equal( 1 );
@@ -432,7 +432,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				expected.position.path = [ 1, 2 ];
 
 				expect( transOp.length ).to.equal( 1 );
@@ -444,7 +444,7 @@ describe( 'transform', () => {
 			it( 'no operation update', () => {
 				const transformBy = new NoOperation( 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -455,7 +455,7 @@ describe( 'transform', () => {
 			it( 'no position update', () => {
 				const transformBy = new RenameOperation( new Position( root, [ 0, 2, 0 ] ), 'oldName', 'newName', 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -467,7 +467,7 @@ describe( 'transform', () => {
 				const newRange = new Range( new Position( root, [ 0, 2, 0 ] ), new Position( root, [ 0, 2, 4 ] ) );
 				const transformBy = new MarkerOperation( 'name', null, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -503,7 +503,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.offset += 2;
 				expected.range.end.offset += 2;
@@ -519,7 +519,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.offset += 2;
 				expected.range.end.offset += 2;
@@ -538,7 +538,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.offset--;
 				expected.range.end.offset--;
@@ -555,7 +555,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.offset += 2;
 				expected.range.end.offset += 2;
@@ -572,7 +572,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -594,7 +594,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -617,7 +617,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.path = [ 2, 4, 2, 1 ];
 				expected.range.end.path = [ 2, 4, 2, 4 ];
@@ -634,7 +634,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 3 );
 
@@ -662,7 +662,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.range.start.path = [ 2, 4, 1 ];
 				expected.range.end.path = [ 2, 4, 4 ];
@@ -679,7 +679,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -701,7 +701,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 3 );
 
@@ -745,7 +745,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -765,7 +765,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -782,7 +782,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -797,7 +797,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -812,7 +812,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -829,7 +829,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -846,7 +846,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expected.oldValue = 'xyz';
 
@@ -864,7 +864,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -875,7 +875,7 @@ describe( 'transform', () => {
 			it( 'no operation update', () => {
 				const transformBy = new NoOperation( 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -886,7 +886,7 @@ describe( 'transform', () => {
 			it( 'no position update', () => {
 				const transformBy = new RenameOperation( new Position( root, [ 0 ] ), 'oldName', 'newName', 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -898,7 +898,7 @@ describe( 'transform', () => {
 				const newRange = new Range( new Position( root, [ 0, 2, 0 ] ), new Position( root, [ 0, 2, 8 ] ) );
 				const transformBy = new MarkerOperation( 'name', null, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -935,7 +935,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -948,7 +948,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -961,7 +961,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.offset += 2;
 
@@ -976,7 +976,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -989,7 +989,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.path[ 1 ] += 2;
 
@@ -1004,7 +1004,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1017,7 +1017,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.offset += 2;
 
@@ -1032,7 +1032,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1045,7 +1045,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.path[ 1 ] += 2;
 
@@ -1060,7 +1060,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1073,7 +1073,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1086,7 +1086,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1099,7 +1099,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1115,7 +1115,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1132,7 +1132,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1149,7 +1149,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1165,7 +1165,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1179,7 +1179,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.offset += 2;
 
@@ -1195,7 +1195,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1209,7 +1209,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.offset -= 2;
 
@@ -1225,7 +1225,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1239,7 +1239,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.path[ 1 ] += 2;
 
@@ -1255,7 +1255,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1269,7 +1269,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.path[ 1 ] -= 1;
 
@@ -1285,7 +1285,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1299,7 +1299,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.offset += 2;
 
@@ -1315,7 +1315,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1329,7 +1329,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.offset -= 2;
 
@@ -1345,7 +1345,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1359,7 +1359,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.path[ 1 ] += 2;
 
@@ -1375,7 +1375,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1389,7 +1389,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.path[ 1 ] -= 2;
 
@@ -1405,7 +1405,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1419,7 +1419,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1439,7 +1439,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1456,7 +1456,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1470,7 +1470,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1484,7 +1484,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.path = [ 4, 3, 4 ];
 
@@ -1500,7 +1500,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.targetPosition.path = [ 0, 2, 3 ];
 
@@ -1516,7 +1516,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 				const reversed = transformBy.getReversed();
 
 				expected.sourcePosition = reversed.sourcePosition;
@@ -1535,7 +1535,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -1551,7 +1551,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expected.sourcePosition.path = [ 4, 1, 0 ];
 
@@ -1567,7 +1567,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -1583,7 +1583,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expected.sourcePosition.path = [ 4, 1, 1 ];
 
@@ -1601,7 +1601,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1621,7 +1621,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1639,7 +1639,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.sourcePosition.path = [ 2, 2, 3 ];
 				expected.howMany = 1;
@@ -1659,7 +1659,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1682,7 +1682,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.howMany = 1;
 
@@ -1698,7 +1698,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1723,7 +1723,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1749,7 +1749,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1773,7 +1773,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.howMany = 1;
 
@@ -1789,7 +1789,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1814,7 +1814,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1840,7 +1840,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1861,7 +1861,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 2 );
 
@@ -1885,7 +1885,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 3 );
 
@@ -1917,7 +1917,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1936,7 +1936,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1959,7 +1959,7 @@ describe( 'transform', () => {
 			} );
 
 			it( 'should skip context.aIsStrong and be less important than MoveOperation', () => {
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -1973,7 +1973,7 @@ describe( 'transform', () => {
 			it( 'no operation update', () => {
 				const transformBy = new NoOperation( 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1984,7 +1984,7 @@ describe( 'transform', () => {
 			it( 'no position update', () => {
 				const transformBy = new RenameOperation( new Position( root, [ 2, 2, 4 ] ), 'oldName', 'newName', 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -1996,7 +1996,7 @@ describe( 'transform', () => {
 				const newRange = new Range( new Position( root, [ 2, 2, 3 ] ), new Position( root, [ 2, 2, 8 ] ) );
 				const transformBy = new MarkerOperation( 'name', null, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2015,7 +2015,7 @@ describe( 'transform', () => {
 
 				const sourcePosition = Position.createFromPosition( transformBy.targetPosition );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2046,7 +2046,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2066,7 +2066,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2083,7 +2083,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2099,7 +2099,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2110,7 +2110,7 @@ describe( 'transform', () => {
 			it( 'no operation update', () => {
 				const transformBy = new NoOperation( 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2121,7 +2121,7 @@ describe( 'transform', () => {
 			it( 'no position update', () => {
 				const transformBy = new RenameOperation( new Position( root, [ 0, 2, 0 ] ), 'oldName', 'newName', 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2133,7 +2133,7 @@ describe( 'transform', () => {
 				const newRange = new Range( new Position( root, [ 0, 2, 0 ] ), new Position( root, [ 0, 2, 8 ] ) );
 				const transformBy = new MarkerOperation( 'name', null, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2162,7 +2162,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2178,7 +2178,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2191,7 +2191,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2207,7 +2207,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2227,7 +2227,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2244,7 +2244,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2256,7 +2256,7 @@ describe( 'transform', () => {
 				const newRange = new Range( new Position( root, [ 0, 2, 0 ] ), new Position( root, [ 0, 2, 8 ] ) );
 				const transformBy = new MarkerOperation( 'name', null, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2272,7 +2272,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2286,7 +2286,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -2302,7 +2302,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2320,7 +2320,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2337,7 +2337,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2354,7 +2354,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2371,7 +2371,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2388,7 +2388,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2405,7 +2405,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 
@@ -2437,7 +2437,7 @@ describe( 'transform', () => {
 				op.newRange = null;
 				const transformBy = new InsertOperation( Position.createAt( root, 0 ), [ nodeA, nodeB ], 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.newRange = null;
 				expected.oldRange.start.offset = 3;
@@ -2452,7 +2452,7 @@ describe( 'transform', () => {
 				op.oldRange = null;
 				const transformBy = new InsertOperation( Position.createAt( root, 8 ), [ nodeA, nodeB ], 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.oldRange = null;
 				expected.newRange.start.offset = 12;
@@ -2476,7 +2476,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2489,7 +2489,7 @@ describe( 'transform', () => {
 				op.newRange = null;
 
 				const transformBy = new MoveOperation( Position.createAt( root, 0 ), 1, Position.createAt( root, 20 ), 0 );
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.newRange = null;
 				expected.oldRange.start.offset = 0;
@@ -2501,7 +2501,7 @@ describe( 'transform', () => {
 
 			it( 'moved range contains oldRange and is before newRange: update oldRange and newRange', () => {
 				const transformBy = new MoveOperation( Position.createAt( root, 2 ), 2, Position.createAt( root, 20 ), 0 );
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.oldRange.start.offset = 1;
 				expected.oldRange.end.offset = 2;
@@ -2517,7 +2517,7 @@ describe( 'transform', () => {
 				op.oldRange = null;
 
 				const transformBy = new MoveOperation( Position.createAt( root, 20 ), 2, Position.createAt( root, 11 ), 0 );
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.oldRange = null;
 				expected.newRange.start.offset = 10;
@@ -2529,7 +2529,7 @@ describe( 'transform', () => {
 
 			it( 'target position is inside oldRange and before newRange: update oldRange and newRange', () => {
 				const transformBy = new MoveOperation( Position.createAt( root, 20 ), 4, Position.createAt( root, 2 ), 0 );
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expected.oldRange.start.offset = 1;
 				expected.oldRange.end.offset = 8;
@@ -2551,7 +2551,7 @@ describe( 'transform', () => {
 					0
 				);
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2562,7 +2562,7 @@ describe( 'transform', () => {
 			it( 'no operation update', () => {
 				const transformBy = new RenameOperation( new Position( root, [ 1 ] ), 'oldName', 'newName', 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2573,7 +2573,7 @@ describe( 'transform', () => {
 			it( 'different marker name: no operation update', () => {
 				const transformBy = new MarkerOperation( 'otherName', oldRange, newRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], expected );
@@ -2583,7 +2583,7 @@ describe( 'transform', () => {
 				const anotherRange = Range.createFromParentsAndOffsets( root, 2, root, 2 );
 				const transformBy = new MarkerOperation( 'name', oldRange, anotherRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy );
+				const transOp = transform( op, transformBy );
 
 				expect( transOp.length ).to.equal( 1 );
 				expectOperation( transOp[ 0 ], {
@@ -2595,7 +2595,7 @@ describe( 'transform', () => {
 				const anotherRange = Range.createFromParentsAndOffsets( root, 2, root, 2 );
 				const transformBy = new MarkerOperation( 'name', oldRange, anotherRange, model.markers, 0 );
 
-				const transOp = transform.transform( op, transformBy, contextIsStrong );
+				const transOp = transform( op, transformBy, strongContext );
 
 				expected.oldRange = anotherRange;
 
diff --git a/tests/model/operation/transform/utils.js b/tests/model/operation/transform/utils.js
index 016842f9c..12cccb7bb 100644
--- a/tests/model/operation/transform/utils.js
+++ b/tests/model/operation/transform/utils.js
@@ -7,7 +7,7 @@ import UndoEditing from '@ckeditor/ckeditor5-undo/src/undoediting';
 import BlockQuoteEditing from '@ckeditor/ckeditor5-block-quote/src/blockquoteediting';
 
 import { getData, parse } from '../../../../src/dev-utils/model';
-import transform from '../../../../src/model/operation/transform';
+import { transformSets } from '../../../../src/model/operation/transform';
 import Position from '../../../../src/model/position';
 import Range from '../../../../src/model/range';
 import OperationFactory from '../../../../src/model/operation/operationfactory';
@@ -290,9 +290,9 @@ export function syncClients() {
 			};
 
 			if ( localClient.orderNumber < remoteClient.orderNumber ) {
-				remoteOperationsTransformed = transform.transformSets( localOperations, remoteOperations, options ).operationsB;
+				remoteOperationsTransformed = transformSets( localOperations, remoteOperations, options ).operationsB;
 			} else {
-				remoteOperationsTransformed = transform.transformSets( remoteOperations, localOperations, options ).operationsA;
+				remoteOperationsTransformed = transformSets( remoteOperations, localOperations, options ).operationsA;
 			}
 
 			localClient.editor.model.enqueueChange( 'transparent', writer => {

From 6dca97ec7e35e2caec8cc954f5c508c17be5a274 Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Thu, 9 Aug 2018 14:28:54 +0200
Subject: [PATCH 25/26] Changed: Make `Schema#getValidRanges` a generator.

---
 src/model/schema.js   | 37 +++++++++++--------------------------
 tests/model/schema.js |  2 +-
 2 files changed, 12 insertions(+), 27 deletions(-)

diff --git a/src/model/schema.js b/src/model/schema.js
index da6a66aa3..180ec353a 100644
--- a/src/model/schema.js
+++ b/src/model/schema.js
@@ -665,19 +665,14 @@ export default class Schema {
 	 *
 	 * @param {Array.<module:engine/model/range~Range>} ranges Ranges to be validated.
 	 * @param {String} attribute The name of the attribute to check.
-	 * @returns {Array.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
+	 * @returns {Iterator.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
 	 */
-	getValidRanges( ranges, attribute ) {
+	* getValidRanges( ranges, attribute ) {
 		ranges = convertToMinimalFlatRanges( ranges );
-		const result = [];
 
 		for ( const range of ranges ) {
-			const validRanges = this._getValidRangesForRange( range, attribute );
-
-			result.push( ...validRanges );
+			yield* this._getValidRangesForRange( range, attribute );
 		}
-
-		return result;
 	}
 
 	/**
@@ -689,22 +684,20 @@ export default class Schema {
 	 * @private
 	 * @param {module:engine/model/range~Range} range Range to process.
 	 * @param {String} attribute The name of the attribute to check.
-	 * @returns {Array.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
+	 * @returns {Iterator.<module:engine/model/range~Range>} Ranges in which the attribute is allowed.
 	 */
-	_getValidRangesForRange( range, attribute ) {
-		const result = [];
-
+	* _getValidRangesForRange( range, attribute ) {
 		let start = range.start;
 		let end = range.start;
 
 		for ( const item of range.getItems( { shallow: true } ) ) {
 			if ( item.is( 'element' ) ) {
-				result.push( ...this._getValidRangesForRange( Range.createIn( item ), attribute ) );
+				yield* this._getValidRangesForRange( Range.createIn( item ), attribute );
 			}
 
 			if ( !this.checkAttribute( item, attribute ) ) {
 				if ( !start.isEqual( end ) ) {
-					result.push( new Range( start, end ) );
+					yield new Range( start, end );
 				}
 
 				start = Position.createAfter( item );
@@ -714,10 +707,8 @@ export default class Schema {
 		}
 
 		if ( !start.isEqual( end ) ) {
-			result.push( new Range( start, end ) );
+			yield new Range( start, end );
 		}
-
-		return result;
 	}
 
 	/**
@@ -1602,15 +1593,9 @@ function* combineWalkers( backward, forward ) {
 // all those minimal flat ranges.
 //
 // @param {Array.<module:engine/model/range~Range>} ranges Ranges to process.
-// @returns {Array.<module:engine/model/range~Range>} Minimal flat ranges of given `ranges`.
-function convertToMinimalFlatRanges( ranges ) {
-	const result = [];
-
+// @returns {Iterator.<module:engine/model/range~Range>} Minimal flat ranges of given `ranges`.
+function* convertToMinimalFlatRanges( ranges ) {
 	for ( const range of ranges ) {
-		const minimal = range.getMinimalFlatRanges();
-
-		result.push( ...minimal );
+		yield* range.getMinimalFlatRanges();
 	}
-
-	return result;
 }
diff --git a/tests/model/schema.js b/tests/model/schema.js
index fd85549a7..890341eb6 100644
--- a/tests/model/schema.js
+++ b/tests/model/schema.js
@@ -1178,7 +1178,7 @@ describe( 'Schema', () => {
 
 			setData( model, '[<p>foo<img></img>bar</p>]' );
 
-			const validRanges = schema.getValidRanges( doc.selection.getRanges(), 'foo' );
+			const validRanges = Array.from( schema.getValidRanges( doc.selection.getRanges(), 'foo' ) );
 
 			expect( validRanges.length ).to.equal( 2 );
 

From 3d9af07b85899c5350dc2118e42b002bd264e99c Mon Sep 17 00:00:00 2001
From: Szymon Cofalik <s.cofalik@cksource.com>
Date: Thu, 9 Aug 2018 14:36:31 +0200
Subject: [PATCH 26/26] Tests: Change the name of helper function.

---
 tests/model/schema.js | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/tests/model/schema.js b/tests/model/schema.js
index 890341eb6..b02a606c8 100644
--- a/tests/model/schema.js
+++ b/tests/model/schema.js
@@ -1121,7 +1121,7 @@ describe( 'Schema', () => {
 			schema.extend( '$text', { allowIn: '$root' } );
 		} );
 
-		function test( input, attribute, output ) {
+		function testValidRangesForAttribute( input, attribute, output ) {
 			setData( model, input );
 
 			const validRanges = schema.getValidRanges( doc.selection.getRanges(), attribute );
@@ -1133,7 +1133,7 @@ describe( 'Schema', () => {
 		it( 'should return a range with p for an attribute allowed only on p', () => {
 			schema.extend( 'p', { allowAttributes: 'foo' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img></img>bar</p>]',
 				'foo',
 				'[<p>foo<img></img>bar</p>]'
@@ -1143,7 +1143,7 @@ describe( 'Schema', () => {
 		it( 'should return ranges on text nodes for an attribute allowed only on text', () => {
 			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img></img>bar</p>]',
 				'bold',
 				'<p>[foo]<img></img>[bar]</p>'
@@ -1153,7 +1153,7 @@ describe( 'Schema', () => {
 		it( 'should return a range on img for an attribute allowed only on img', () => {
 			schema.extend( 'img', { allowAttributes: 'src' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img></img>bar</p>]',
 				'src',
 				'<p>foo[<img></img>]bar</p>'
@@ -1164,7 +1164,7 @@ describe( 'Schema', () => {
 			schema.extend( '$text', { allowAttributes: 'bold' } );
 			schema.extend( 'img', { allowAttributes: 'bold' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img></img>bar</p>]',
 				'bold',
 				'<p>[foo<img></img>bar]</p>'
@@ -1192,7 +1192,7 @@ describe( 'Schema', () => {
 		it( 'should not break a range if children are not allowed to have the attribute', () => {
 			schema.extend( 'p', { allowAttributes: 'foo' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo</p><p>bar</p>]',
 				'foo',
 				'[<p>foo</p><p>bar</p>]'
@@ -1202,7 +1202,7 @@ describe( 'Schema', () => {
 		it( 'should search deeply', () => {
 			schema.extend( '$text', { allowAttributes: 'bold', allowIn: 'img' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img>xxx</img>bar</p>]',
 				'bold',
 				'<p>[foo]<img>[xxx]</img>[bar]</p>'
@@ -1212,7 +1212,7 @@ describe( 'Schema', () => {
 		it( 'should work with multiple ranges', () => {
 			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>a</p><p>b</p>]<p>c</p><p>[d]</p>',
 				'bold',
 				'<p>[a]</p><p>[b]</p><p>c</p><p>[d]</p>'
@@ -1222,7 +1222,7 @@ describe( 'Schema', () => {
 		it( 'should work with non-flat ranges', () => {
 			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>a</p><p>b</p><p>c]</p><p>d</p>',
 				'bold',
 				'<p>[a]</p><p>[b]</p><p>[c]</p><p>d</p>'
@@ -1232,7 +1232,7 @@ describe( 'Schema', () => {
 		it( 'should not leak beyond the given ranges', () => {
 			schema.extend( '$text', { allowAttributes: 'bold' } );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo</p><p>b]a[r</p><p>x]yz</p>',
 				'bold',
 				'<p>[foo]</p><p>[b]a[r]</p><p>[x]yz</p>'
@@ -1249,7 +1249,7 @@ describe( 'Schema', () => {
 				}
 			} );
 
-			test(
+			testValidRangesForAttribute(
 				'[<p>foo<img>xx]x</img>bar</p>',
 				'bold',
 				'<p>[foo]<img>xxx</img>bar</p>'