Anti-pattern #2: The unit test is written so poorly that you have no idea if it's important anymore or not.
Solution: Get in the wayback machine and whack yourself upside the head as you write that unit test in the first place.
An obscure test would have made it easy to disclaim as "invalid", but this test was so simple and understandable, it was an outright self-lie that I wanted to be believe it to be invalid.
Had it not been readable, the path taken could have been different - for the worse.
So, one other solution: make sure your test is *not* obscure so that the truth hits you in the face when you see it - the test is indeed valid.