A few weeks ago, I was working through an issue with one of the projects Im responsible for. Basically, we have a collection of id/name pairs that needed to be sorted alphabetically by name.
I started working through how to attack this problem and ended up with an absolutely over-designed solution, involving 4 different objects and approximately 200 lines of code. I thought that surely there had to be a better way of solving this problem, so I shelved what I had and started over using TDD.
I wrote one test at a time, writing just enough code to make the test pass. In the end, I have one very well tested class that is responsible for sorting these items. Amount of production code: 14 lines. Clearly a better solution.
Interestingly enough, I saw a similar result from Robert Martin's presentation at our organization last week when he went through his TDD example to calculate bowling scores.