What is Test Driven Development (TDD)?
Testing methodology associated with Agile Programming in which every chunk of code is covered by unit tests, which must all pass all the time, in an effort to eliminate unit-level and regression bugs during development. Practitioners of TDD write a lot of tests, i.e. an equal number of lines of test code to the size of the production code.
TestDriven.NET is a good testing tools used for TDD.
Other TDD resources: