If you're expecting it to fail then your brain is already doing the work that the test is meant to do. It serves as an expensive to-do reminder in that scenario

If you're expecting it to fail then your brain is already doing the work that the test is meant to do. It serves as an expensive to-do reminder in that scenario. If you are part way or all the way through your refactor and think you're on the right track and then you unexpectedly have a failing test, then I would say that that was a useful bit of test code.