Often I see tests that spend a lot of time mocking internal components of the application. Such tests are verifying the implementation details instead of the functionality. They often need to be thrown out if you do some refactoring, even if that refactoring didn’t change the behavior of the program at all. The kind of text described in this article should work just fine in that case, achieving the desired goal of showing whether your refactor caused any behavior changes.

In my experience, tests like this actually aren’t hard to maintain. The test can print out a diff between the expected and actual result when there is a failure, so you can check if the new behavior is expected and easily copy-paste to update the test if desired.