diff --git a/dev/src/BaselineOfExercism/BaselineOfExercism.class.st b/dev/src/BaselineOfExercism/BaselineOfExercism.class.st
index 6c776065..bbc53725 100644
--- a/dev/src/BaselineOfExercism/BaselineOfExercism.class.st
+++ b/dev/src/BaselineOfExercism/BaselineOfExercism.class.st
@@ -67,6 +67,11 @@ BaselineOfExercism >> baseline: spec [
 				group: 'testRunner' with: #('ExercismTestRunner');
 				group: 'testRunnerTests' with: #('ExercismTestRunnerTests'), self class exerciseGoldenTestPackageNames;
 				group: 'v3' with: #('ExercismV3')
+			].
+			spec for: #'pharo12.x' do: [
+				"ExercismTools methods will be overwritten by compatibility package for Pharo 12"
+				spec package: 'ExercismTools' with: [ spec includes: #('ExercismPharo120') ].
+				spec package: 'ExercismPharo120' 
 			]
 ]
 
diff --git a/dev/src/ExercismPharo120/ExercismSubmissionTest.extension.st b/dev/src/ExercismPharo120/ExercismSubmissionTest.extension.st
new file mode 100644
index 00000000..bb28bb39
--- /dev/null
+++ b/dev/src/ExercismPharo120/ExercismSubmissionTest.extension.st
@@ -0,0 +1,103 @@
+Extension { #name : #ExercismSubmissionTest }
+
+{ #category : #'*ExercismPharo120' }
+ExercismSubmissionTest class >> mockSnapshotSTON [
+^	'MCSnapshot {
+	#definitions : OrderedCollection [
+		MCOrganizationDefinition {
+			#packageName : #''Exercise@DependencyMock'',
+			#tagNames : [ ]
+		},
+		MCMethodDefinition {
+			#classIsMeta : false,
+			#source : ''mockMethod ^ \''Call from class: \'', self class name'',
+			#category : #''as yet unclassified'',
+			#selector : #mockMethod,
+			#className : #CMock
+		},
+		MCMethodDefinition {
+			#classIsMeta : false,
+			#source : ''mockMethod ^ CMock mockMethod'',
+			#category : #''as yet unclassified'',
+			#selector : #mockMethod,
+			#className : #BMock
+		},
+		MCMethodDefinition {
+			#classIsMeta : false,
+			#source : ''mockMethod ^ BMock mockMethod'',
+			#category : #''as yet unclassified'',
+			#selector : #mockMethod,
+			#className : #AMock
+		},
+		MCClassDefinition {
+			#name : #CMock,
+			#superclassName : #Object,
+			#variables : OrderedCollection [ ],
+			#packageName : #''Exercise@DependencyMock'',
+			#type : #normal,
+			#comment : '''',
+			#commentStamp : '''',
+			#traitComposition : ''{}'',
+			#classTraitComposition : ''{}''
+		},
+		MCClassDefinition {
+			#name : #BMock,
+			#superclassName : #CMock,
+			#variables : OrderedCollection [ ],
+			#packageName : #''Exercise@DependencyMock'',
+			#type : #normal,
+			#comment : '''',
+			#commentStamp : '''',
+			#traitComposition : ''{}'',
+			#classTraitComposition : ''{}''
+		},
+		MCClassDefinition {
+			#name : #AMock,
+			#superclassName : #BMock,
+			#variables : OrderedCollection [ ],
+			#packageName : #''Exercise@DependencyMock'',
+			#type : #normal,
+			#comment : '''',
+			#commentStamp : '''',
+			#traitComposition : ''{}'',
+			#classTraitComposition : ''{}''
+		}
+	],
+	#classDefinitionCache : {
+		#AMock : @12,
+		#CMock : @8,
+		#BMock : @10
+	}
+}'
+]
+
+{ #category : #'*ExercismPharo120' }
+ExercismSubmissionTest class >> prepareMockPackageWithDependentClasses [
+" this is used for generating STON representation of MCSnapshot (see class side method), we don't need to create classes during test"
+|aClass bClass cClass aPackage|
+
+	cClass := Object << #CMock
+		slots: {};
+		sharedVariables: {};
+		package: 'Exercise@DependencyMock';
+		install.
+		
+	bClass := (self class environment at: #CMock) << #BMock
+		slots: {};
+		sharedVariables: {};
+		package: 'Exercise@DependencyMock';
+		install.
+
+	aClass := (self class environment at: #BMock) << #AMock
+		slots: {};
+		sharedVariables: {};
+		package: 'Exercise@DependencyMock';
+		install.
+
+	aClass compile: 'mockMethod ^ BMock mockMethod'.
+	bClass compile: 'mockMethod ^ CMock mockMethod'.
+	cClass compile: 'mockMethod ^ ''Call from class: '', self class name'.
+
+	aPackage := PackageOrganizer default packageNamed: 'Exercise@DependencyMock'.
+	^ TonelWriter new toSTON: aPackage snapshot.
+]
diff --git a/dev/src/ExercismPharo120/package.st b/dev/src/ExercismPharo120/package.st
new file mode 100644
index 00000000..dd7630d8
--- /dev/null
+++ b/dev/src/ExercismPharo120/package.st
@@ -0,0 +1 @@
+Package { #name : #ExercismPharo120 }
diff --git a/dev/src/ExercismTests/ExercismExerciseTest.class.st b/dev/src/ExercismTests/ExercismExerciseTest.class.st
index 14fd8483..49daebe6 100644
--- a/dev/src/ExercismTests/ExercismExerciseTest.class.st
+++ b/dev/src/ExercismTests/ExercismExerciseTest.class.st
@@ -163,9 +163,9 @@ ExercismExerciseTest >> testSolutionSources [
 	
 	self assertCollection: sources keys asSet equals: classNames asSet.
 	
-	(sources at: classNames last) should includeSubstring: 'Tested on:'.
-	(sources at: classNames first) should includeSubstring: '#name : #', classes first name.
-	(sources at: classNames allButLast last) should includeSubstring: '#name : #', classes last name.
+	(sources at: classNames last) includesSubstring: 'Tested on:'.
+	(sources at: classNames first) includesSubstring: '#name : #', classes first name.
+	(sources at: classNames allButLast last) includesSubstring: '#name : #', classes last name.
 ]
 
 { #category : #tests }