Just like in math, even if the code is provably correct, there is always the possibility someone screwed up the proof. In the end it always comes down to writi

Just like in math, even if the code is provably correct, there is always the possibility someone screwed up the proof. In the end it always comes down to writing the least buggy software possible and then bug zapping. Having debug tools is smart of course, but TDD goes a bit further than debug tools. When I write unit tests I don't think of them as unit tests I think of them as debugging probes.