> If you define a functional test as perfect, that it will never break unless the actual functionality changes, then sure, functional tests are purely good. But that's not what most people end up writing when they try to write functional tests. They don't get them right, they write code-change tests.

What is your experience with fixing this issue as it arises? Like you see the test breaking and say "Oh the output changed but it still satisfies <important property>, let's change the test to be more general!". Or more drastically "this test keeps having false alarms, let's just remove it".