Start writing tests the moment you have something to lose. Earlier if you like, but no later than that moment. Tests are about system integrity. If you risk lo

Start writing tests the moment you have something to lose. Earlier if you like, but no later than that moment. Tests are about system integrity. If you risk losing something due to lack of integrity, tests are worth your while. Think of it like health insurance: When are you comfortable forgoing health insurance, and when are you not?