Merge branch 't/12841'

Author: Reinmar

tests/_benderjs/ckeditor/static/extensions.js

@@ -102,6 +102,7 @@
 		if ( expected < min || expected > max ) {
 			throw new YUITest.ComparisonFailure(
 				YUITest.Assert._formatMessage( message ),
+				'Greater than ' + min + ' and lower than ' + max + '.',
 				expected
 			);
 		}

tests/utils/assert/isnumberinrange.js

@@ -40,6 +40,17 @@
 			assert.isNumberInRange( 100, 99, 101, '99 <= 100 <= 101' );
 			assert.isNumberInRange( 100, 100, 101, '100 <= 100 <= 101' );
 			assert.isNumberInRange( 100, 98, 100, '98 <= 100 <= 100' );
+		},
+
+		// #12841
+		'test proper assertion message': function() {
+			try {
+				assert.isNumberInRange( 102, 99, 101, 'Custom message.' );
+			} catch ( e ) {
+				assert.areEqual( 'Custom message.', e.message );
+				assert.areEqual( 'Greater than 99 and lower than 101.', e.expected );
+				assert.areEqual( 102, e.actual );
+			}
 		}
 	} );
-} )();
+} )();