Made String >> hasSubstring:at: more robust for a variety of situatio…

…ns detailed in the tests.

src/Collections-Strings-Tests/StringTest.class.st

@@ -1260,6 +1260,24 @@ StringTest >> testFormatFailures [
 
 ]
 
+{ #category : #test }
+StringTest >> testHasSubstringAt [
+
+	"Test empty strings"
+	self assert: ('' hasSubstring: '' at: 1).
+	self assert: ('test' hasSubstring: '' at: 1).
+	self deny: ('' hasSubstring: 'test' at: 1).
+	"Test out of bounds indexes"
+	self deny: ('test' hasSubstring: 't' at: 0).
+	self deny: ('test' hasSubstring: 't' at: 10).
+	"Test matching substring"
+	self assert: ('test' hasSubstring: 'st' at: 3).
+	"Test partially matching substring"
+	self deny: ('test' hasSubstring: 'sty' at: 3).
+	
+	
+]
+
 { #category : #tests }
 StringTest >> testHasWideCharacterFromTo [
 

src/Collections-Strings/String.class.st

@@ -1601,12 +1601,14 @@ String >> hasSubstring: str at: index [
 	"Answer true if the receiver contains the substring str exactly at index, false otherwise."
 
 	| pos |
+	
+	(index < 1) ifTrue: [ ^ false ].
 	pos := index - 1.
-
+	
 	^ str size <= (self size - pos) and:
-		[ str allSatisfy: [ :char | 
+		[ str noneSatisfy: [ :char |  
 		  pos := pos + 1.
-		  (self at: pos) = char ] ]
+		  (self at: pos) ~= char ] ]
 ]
 
 { #category : #testing }