IMHO, precious moment when bug is found in the code AND it is not obvious, so you need to run debugger, is perfect time to improve your code. It indicates that

IMHO, precious moment when bug is found in the code AND it is not obvious, so you need to run debugger, is perfect time to improve your code. It indicates that code is complicated, or not well covered, or poorly commented (because bug is not noticed at peer review). You are going to test this piece of code anyway, because you need to check is bug fixed, so why not to spare some time to make code better and battle-test your improvement: if you catch bug in the process, then you improved code, if not: keep going. And no, I am not talking about asserts. Assertions are only small part of real debugger. Typical tools I use in my own programs are: good logging and tracing, which are able to explain what happens inside program without spamming me, some test cases for critical parts and for fixed bugs. Often, I will also split large program or script into smaller independent parts, with their own options, configuration, loggind and test cases. It's all.