In this post, I will show you why it is important to use Unit Testing, how to use it and how to avoid writing the same code 2 times. Also, i will show you how to do a basic Test Driven Development with SimpleTest and Zend Framework 1.10. Also, this tutorial will show you how to directly link your tests to the code of your application, without duplicating content. At the end, you will be able to extend the tests to run on any code you write.