This document introduces unit testing in PHP and Magento. It discusses what unit testing is, why it is important, and how it can help catch bugs and allow code to be refactored more easily. It then introduces PHPUnit as the de facto unit testing framework for PHP. Key PHPUnit techniques like assertions and mocking are covered. Finally, it discusses how the Magento PHPUnit integration extension allows unit testing of Magento code and modules using PHPUnit. Demo code is referenced to illustrate unit testing concepts and techniques.