The problem is, Extreme Programming is promoted as the approach to use when you don't know what your final result will be like. "Embrace Change!" As far as I understand, Jeffries was not being stupid in that series of posts. He could have looked up the right algorithms at any time, like you or me. He was just trying to make an honest showcase for his own methodology which says you're supposed to be comfortable not knowing exactly where you're going. It was an experiment worth trying, and if it worked it would've helped convince me that TDD is widely useful. Like that famous presentation where Ocaml's type system catches an infinite loop.