I recommend the following strategy: 1. Don’t ship any new features without writing unit tests for them first. 2. These new features most likely rely on parts

I recommend the following strategy: 1. Don’t ship any new features without writing unit tests for them first. 2. These new features most likely rely on parts of existing code so write a few tests for that existing code with each new feature. 3. If something breaks in production write a test for it at the time that you fix it. Little by little you’ll increase your code coverage without grinding development to a halt.