This is a presentation for a lunchtime brownbag session I gave to my ThoughtWorks colleagues on the Growing Object-Oriented Software Guided by Tests (GOOS) book http://www.amazon.co.uk/Growing-Object-Oriented-Software-Guided-Signature/dp/0321503627/ref=sr_1_1?ie=UTF8&qid=1367081921&sr=8-1&keywords=growing+object-oriented+software+guided+by+tests