diff --git a/src/Framework/MockObject/MockBuilder.php b/src/Framework/MockObject/MockBuilder.php
index 3d26278caae..b083ba202e7 100644
--- a/src/Framework/MockObject/MockBuilder.php
+++ b/src/Framework/MockObject/MockBuilder.php
@@ -296,7 +296,7 @@ public function addMethods(array $methods): self
             if ($reflector->hasMethod($method)) {
                 throw new RuntimeException(
                     \sprintf(
-                        'Trying to set mock method "%s" with addMethod, but it exists in class "%s". Use onlyMethods() for methods that exist in the class.',
+                        'Trying to set mock method "%s" with addMethods, but it exists in class "%s". Use onlyMethods() for methods that exist in the class.',
                         $method,
                         $this->type
                     )
diff --git a/tests/unit/Framework/MockObject/MockBuilderTest.php b/tests/unit/Framework/MockObject/MockBuilderTest.php
index 158dd117492..8b97496d835 100644
--- a/tests/unit/Framework/MockObject/MockBuilderTest.php
+++ b/tests/unit/Framework/MockObject/MockBuilderTest.php
@@ -63,6 +63,7 @@ public function testSetMethodsAllowsNonExistentMethodNames(): void
     public function testOnlyMethodsWithNonExistentMethodNames(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Trying to set mock method "mockableMethodWithCrazyName" with onlyMethods, but it does not exist in class "Mockable". Use addMethods() for methods that don\'t exist in the class.');
 
         $this->getMockBuilder(Mockable::class)
              ->onlyMethods(['mockableMethodWithCrazyName'])
@@ -91,6 +92,7 @@ public function testOnlyMethodsWithEmptyArray(): void
     public function testAddMethodsWithNonExistentMethodNames(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Trying to set mock method "mockableMethod" with addMethods, but it exists in class "Mockable". Use onlyMethods() for methods that exist in the class.');
 
         $this->getMockBuilder(Mockable::class)
              ->addMethods(['mockableMethod'])
@@ -129,6 +131,7 @@ public function testEmptyMethodExceptionsToMockCanBeSpecified(): void
     public function testNotAbleToUseAddMethodsAfterOnlyMethods(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Cannot use addMethods() on "Mockable" mock because mocked methods were already configured.');
 
         $this->getMockBuilder(Mockable::class)
              ->onlyMethods(['mockableMethod'])
@@ -139,6 +142,7 @@ public function testNotAbleToUseAddMethodsAfterOnlyMethods(): void
     public function testNotAbleToUseOnlyMethodsAfterAddMethods(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Cannot use onlyMethods() on "Mockable" mock because mocked methods were already configured.');
 
         $this->getMockBuilder(Mockable::class)
              ->addMethods(['mockableMethodWithFakeMethod'])
@@ -169,6 +173,7 @@ public function testAbleToUseSetMethodsAfterAddMethods(): void
     public function testNotAbleToUseAddMethodsAfterSetMethods(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Cannot use addMethods() on "Mockable" mock because mocked methods were already configured.');
 
         $this->getMockBuilder(Mockable::class)
               ->setMethods(['mockableMethod'])
@@ -179,6 +184,7 @@ public function testNotAbleToUseAddMethodsAfterSetMethods(): void
     public function testNotAbleToUseOnlyMethodsAfterSetMethods(): void
     {
         $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Cannot use onlyMethods() on "Mockable" mock because mocked methods were already configured.');
 
         $this->getMockBuilder(Mockable::class)
              ->setMethods(['mockableMethodWithFakeMethod'])