I run a one-man project and I write test first unit tests for all of my code. This has enabled me to advance the code with new functions without breaking curren

I run a one-man project and I write test first unit tests for all of my code. This has enabled me to advance the code with new functions without breaking current API’s. The tests are not in the way and usually doesn’t need to change because I change the implementation. It has been tremendous for productivity because I don’t need to worry about if stuff breaks. I can trust my tests for changing those and so far they have always done that.