This document discusses unit testing PHP code. It begins by introducing the author and their experience with PHP and WordPress. It then discusses different types of testing including functionality, integration, and unit testing. The bulk of the document focuses on unit testing PHP code using PHPUnit - it discusses installing and setting up PHPUnit, writing test classes and methods, the three steps of setup, act, and verify in test cases, and using mocks in tests. The document provides examples of writing PHPUnit tests and ends by listing some PHPUnit tips.