I've read the Microsoft paper, and I'm not clear on something: The paper is comparing TDD vs non-TDD groups... but what are the non-TDD groups doing? Are they

I've read the Microsoft paper, and I'm not clear on something: The paper is comparing TDD vs non-TDD groups... but what are the non-TDD groups doing? Are they test last? Are they ad-hoc? Do they test at all? Did I misread something? Also, Greg Wilson's video is excellent.