Hobbyist vs Professional

What separates hobbyist coders from professional developers? Testing and debugging. On a real job you write far less new code than you'd expect, most of your time goes to figuring out why code doesn't work and making careful changes to an existing codebase. The developers who get hired and promoted to senior are the ones who can take a bug report, reproduce it, isolate the cause, and fix it without breaking other things or complaining to management. And this matters more than ever with AI, because it generates so much code you can't test it all by hand, so you need a deeper grasp of testing