Better comment and a few more test assertions

src/Collections-Sequenceable-Tests/IntervalTest.class.st

@@ -638,13 +638,16 @@ IntervalTest >> testRangeIncludes [
 
 	self assert: ((1 to: 10) rangeIncludes: 3).
 	self assert: ((1 to: 10 by: 2) rangeIncludes: 3).
-	self assert: ((1 to: 10 by: 2) rangeIncludes: 4).
 	self assert: ((10 to: 1 by: -2) rangeIncludes: 3).
+	self assert: ((1 to: 10 by: 2) rangeIncludes: 4).
+	self assert: ((1 to: 10) rangeIncludes: 3.5).
 
 	self deny: ((1 to: 10) rangeIncludes: 0).
 	self deny: ((1 to: 10) rangeIncludes: 11).
 	self deny: ((1 to: 10 by: 2) rangeIncludes: 0).
-	self deny: ((1 to: 10 by: 2) rangeIncludes: 11)
+	self deny: ((1 to: 10 by: 2) rangeIncludes: 11).
+	self deny: ((10 to: 1) rangeIncludes: 3).
+	self deny: ((10 to: 1) rangeIncludes: -3)
 ]
 
 { #category : #tests }

src/Collections-Sequenceable/Interval.class.st

@@ -312,8 +312,11 @@ Interval >> printOn: aStream [
 
 { #category : #testing }
 Interval >> rangeIncludes: aNumber [
-	"Return true if the number lies in the interval between start and stop, considering all values in between as if step was either +1 or -1.
-	Use #include: to take the exact step into account."
+	"Return true if aNumber lies anywhere between the interval bounds.
+	This is a fast O(1) bounds check.
+	
+	Beware: because #rangeIncludes: only considers the sign of the step, not its magnitude, it also returns true for values that are not actual elements of the interval.
+	For precise element inclusion with arbitrary step, use #includes:."
 
 	^ step >= 0
 		ifTrue: [ aNumber between: start and: stop ]