So much for the case for fixing bugs as early as possible, testing as much as possible before release. and TDD being a tool to help with that….
Though the point of having a TestSuite is that it reduces the amount of context, you have to upload into your brain, when you modify/add functionality to old code. Giving one look at the test cases will give you a better idea than reading through the code to figure out what changes will affect what related features. Test-Driven is one extreme form of doing it and is not recommended for everyone.