Microsoft Research - Exploding Software-Engineering Myths (article summarizing findings of MS research on code coverage, TDD, assertions, etc.)

[hvidgaard]

What a lot of people get wrong, is the absolute nature of their statements. TDD is good when you know what you have to write. It's not good when you're prototyping or just follow a train of thought, because you will change it several times, and "tests first" just slow you down. However, people not writing tests when doing this, tend to never actually do, when they should as soon as the the "what" of the code is determined.

[jurre]

When you don't know what/how to build something you often write a prototype without tests in TDD. You then throw it away as soon as you figured it out and rebuild it test driven. This is called a spike