“But I can write my tests later,” you say. No, you can’t. Not really. Oh, you can write some tests later. You can even approach high coverage later if you are careful to measure it. But the tests you write after the fact are defense. The tests you write first are offense. After-the-fact tests are written by someone who is already vested in the code and already knows how the problem was solved. There’s just no way those tests can be anywhere near as incisive as tests written first.
