Test-driven development (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. What is the primary goal of TDD? One view is the goal of TDD is specification and not validation (Martin, Newkirk, and Kess 2003). In other words, it’s one way to think through your requirements or design before your write your functional code (implying that TDD is both an important agile requirements and agile design technique).
SimpleTest - Unit Testing for PHP
Planning User stories are written. Release planning creates the release schedule.
10 Steps for Setting up an Agile Start-up « The Agile Executive
What's the problem? Here at Google, we have thousands of engineers working on our code base every day. In fact, as previously noted, 50% of the Google code base changes every month. That’s a lot of code and a lot of people. In order to ensure that our code base stays healthy, Google primarily employs unit testing and code review for all new check-ins. Bug Prediction at Google