> After the changes, you know there's probably bugs, but you don't know where. Which highlights one of the "problems" with unit tests: if something fails, you

> After the changes, you know there's probably bugs, but you don't know where. Which highlights one of the "problems" with unit tests: if something fails, you have to take time to go and fix it. If you have no tests, you can assume there are no bugs because you are such a great programmer, then go home after a job well done. That there actually are bugs there doesn't bother you, because you don't know about them. It takes less time to write buggy code.