As is mentioned on the Zend Developer Zone, Nick Belhomme has released the first few pages of the training materials he's created for using PHPUnit effectively in testing applications for free.

Today is an awesome day my dear fellow programmers. Today is the day I decide to freely distribute the first couple of pages of the PHPUnit workshop I have been giving for some time now. It is a workshop that builds a small demo application the Test Driven Development way. The reason I open this workshop course is because I strongly believe everybody should understand and use PHPUnit in their projects.

The free content is hosted off of SlideShare and covers some of the basics of testing including how to use PHPUnit and things like test doubles and handling dependencies.