Yes, debug logs are my usual m.o. too. In general I follow the divide-and-conquer approach for localizing the source of a bug - it works well for > 95% of bugs.

Yes, debug logs are my usual m.o. too. In general I follow the divide-and-conquer approach for localizing the source of a bug - it works well for > 95% of bugs. If you're using an interpreted language, a REPL is brilliant for debugging individual functions (I use this mostly with Lisp, but also to some extent with Python). Disclaimer: I'm not a professional dev...