> Writing quality tests for existing code is much harder than writing tests for code that doesn't exist I’ve been trying this and the biggest place it’s helped

> Writing quality tests for existing code is much harder than writing tests for code that doesn't exist I’ve been trying this and the biggest place it’s helped me is parsing. Working out all the bad formats, types, unexpected stuff before I write the code was worth it. It’s still probably low quality compared to what it will eventually be, but a pretty good way to start.