[3am]

Well.. I disagree, but I wouldn't have downvoted you because it's a fair point.

It's a bad idea for developers to QA their own code for a number of reasons. 1) Developers have cognitive blinders, like everyone else. They might not test for something that they is unlikely 2) Some errors can be impractical to catch outside of top level integration testing (getting into unexpected states in state machines or race conditions) 3) There is a conflict of interest between deadlines and meeting requirements.

I have seen companies reach 100+ developers using this approach, conclude it's unsustainable, and be forced to make exceptional efforts to build a QA team. I believe reason 3 is the biggest risk.