Your situation is the best opportunity to add tests, IMO. The codebase is mature and it's architecture is likely well established. It's easier to write tests f

Your situation is the best opportunity to add tests, IMO. The codebase is mature and it's architecture is likely well established. It's easier to write tests for small changes in a very established system than it is to write tests for a system that's still in flux. In most cases that I've seen, this isn't done because there's no financial upside to doing so. When your bonus is tied to velocity, not quality, any effort on testing is too much effort.