In Test-Driven Development (TDD) , The writing of a unit test is done more to design and to document than to verifiy. By writing a unit test you close a number of feedback loops, and verifying the functionality of the code is just a minor one. everything you need to know about your class under test is embodied in a simple list of the names of the tests. Michael Sorens continues his introduction to TDD that is more of a journey in six parts, by discussing Tests as Documentation, False Positive Results and Component Isolation.