I had a coworker who was obsessed with writing unit tests. He was the lead developer on a project which was supposed to take three months and at one point had gone past the two year mark without producing working code. At one point during a meeting with the increasingly (and legitimately) unhappy client, he blurted out “but we’ve written six times as much test code as actual code!” He was not exaggerating either. Believe it or not, this made the client even less happy.