Test-driven design (TDD) (Beck 2003; Astels 2003), is an evolutionary approach to development which combines test-first development where you write a test before you write just enough production code to fulfill that test and refactoring.
A good approach is to add an xUnit test first, it would then fail until you refactor and implement the functionality. This goes on iteratively and continuously. The benefit is that the business requirements are converted to test cases which will be then use during the QA Testing. This will avoid guessworks on the side of the QA analysts
