Great explanation of 'how' but could have done with a bit more info one exactly 'why' to do things like this.

As far as I can see, writing the test first is a waste of time if it is being done by the same person as is developing the code: if you know what to test for, then you know how to write code that will pass, and will stop improving the code when it passes all of the tests.

By testing after the code is written, you get a chance to write additional tests when you have seen odd behaviour.

If you have the luxury of a seperate testing team, then there is no point bringing them in before any code has been written - that is what a design is supposed to be for!