Stub/mock rules move createMock() → createStub() when a mock has no expectations. But a variable can be passed to a local helper method that requires MockObject and calls expects() on it — there a stub is a type error.

This rule fixes those spots back:

 public function testNotificationOfUnpublishToAuthor(): void
 {
     $event = new Event();
-    $user  = $this->createStub(User::class);
+    $user  = $this->createMock(User::class);
     $this->prepareCommonMocks($event, $user);
 }

 /**
  * @param MockObject&User $user
  */
 private function prepareCommonMocks(Event $event, MockObject $user): void
 {
     $user->expects($this->once())
         ->method('getId')
         ->willReturn(1);
 }

Real-world case: mautic/mautic NotificationHelperTest

Only triggers when the variable is passed as an argument to a method/static call whose parameter type is MockObject — native type, docblock intersection, positional or named argument. A stub used only for method()/willReturn() is left alone.

Registered in phpunit110.php and phpunit-mock-to-stub.php sets. No ping-pong with ExpressionCreateMockToCreateStubRector, which already skips variables passed to MockObject params.