NUnit is a MUST. I wonder why you say unfortunately. I realize it's not the most popular thing on the HN block but if you're not proud of your codebase, it's

NUnit is a MUST. I wonder why you say unfortunately. I realize it's not the most popular thing on the HN block but if you're not proud of your codebase, it's never going to work. Since you have NO automated tests, start this way: 1) Every single time someone fixes a bug or adds a new feature, they MUST have at least one automated test that "proves" this functionality is correct 2) In your "spare" time, you can also write automated tests to test the code execution paths covered in your manual tests that I assume you run As for what to skip, at the beginning: nothing. Try testing -everything- you touch. You need all you can to get some real regression testing in. Eventually when you are at 50-70% code coverage you will be in a position to know what are the high-value things to cover and maybe pick and choose (although probably not).