Learn essential PHP testing skills in this comprehensive tutorial on PHPUnit Test Doubles. Discover how to replace PHP objects with mock objects for isolated code testing. Explore the differences between PHPUnit Stubs and PHPUnit MockObjects, and master various techniques to simplify your testing process. Cover topics such as creating mock objects, setting expectations, faking method returns, handling exceptions, using callbacks for complex returns, testing method arguments, and creating custom mocks with the Mock Builder. Gain practical knowledge to enhance your PHP testing capabilities and improve your overall code quality.