TDD (Test Driven Development) is an amazing Software Design and Development methodology that revolutionises the way that you build Software.

When Doing TDD you are trying to Isolate your SUT (System Under Test). To do this you typically create Test Doubles (see previous blog) either automatically with a tool such as RhinoMocks or manually (i.e. you hand code the TestDouble).

When using Microsofts Latest addition to the plethora of IOC Container Unity I kept running into the annoying 'ResolutionFailedException' this is a really frightening error with an obscure error message and it is really not obvious what the problem is.

Peer programming with an Intermediate today and I called my Test Double a xxxxSpy. My Peer immediately asked me why? I quickly ran a survey with several friends who all do TDD and realised that the difference between different types of Test Doubles is not well understood.

Since I am a believer that a common language helps communication I decided to quickly write this blog. It mostly contains references to other peoples excellent writtings on these topics.