Well I've had projects where I've written a lot of tests before really having the overall design right (without realizing it of course) and ended up wishing I'd

Well I've had projects where I've written a lot of tests before really having the overall design right (without realizing it of course) and ended up wishing I'd waited a bit before writing the tests, because I had to redo a lot of them and it slowed down the process. Of course if you just do things right from the start this won't happen, but I often don't.