diff --git a/src/Moco-U2D-Tests/MocoUmlMediatingClassOptimizationTransformationRuleTest.class.st b/src/Moco-U2D-Tests/MocoUmlMediatingClassOptimizationTransformationRuleTest.class.st
new file mode 100644
index 0000000..c59bb4e
--- /dev/null
+++ b/src/Moco-U2D-Tests/MocoUmlMediatingClassOptimizationTransformationRuleTest.class.st
@@ -0,0 +1,39 @@
+Class {
+	#name : #MocoUmlMediatingClassOptimizationTransformationRuleTest,
+	#superclass : #MocoTransformationRuleTestCase,
+	#category : #'Moco-U2D-Tests-Rule'
+}
+
+{ #category : #'private - processing' }
+MocoUmlMediatingClassOptimizationTransformationRuleTest >> execute [
+	^ self execute: MocoUmlMediatingClassOptimizationTransformationRule
+]
+
+{ #category : #tests }
+MocoUmlMediatingClassOptimizationTransformationRuleTest >> testOptimization [
+	| class table pk |
+	class := MocoUmlClass new.
+	table := MocoRdbTable new.
+	
+	table columns add: (MocoRdbColumn new name: 'ID'; yourself).
+	table constraints add: (MocoRdbPrimaryKey new name: 'PK'; yourself).
+	table constraints first columns add: (table columns first).
+	
+	table columns add: (MocoRdbColumn new name: 'FK'; yourself).
+	table constraints add: (MocoRdbForeignKey new name: 'FK'; yourself).
+	table constraints second columns add: (table columns second).
+	
+	(engine input) addElement: class; metaOf: class at: #generatedBy put: #MocoUmlManyToManyAssociationTransformationRule.
+	engine addOutputElement: table withSource: class.
+	
+	self execute.
+	
+	self assert: (table columns size) equals: 1.
+	
+	pk := table constraints select: [ :each | each isKindOf: MocoRdbPrimaryKey ].
+	self assert: (pk size) equals: 1.
+	pk := pk first.
+	
+	self assert: (pk columns size) equals: 1;
+		assert: (pk columns first) identicalTo: (table columns first)
+]