On his blog today Sebastian Bergmann shows how to use PHPUnit from a git checkout and run its own suite of tests easily.
Users of PHPUnit frequently ask me questions such as "How do I use PHPUnit from a Git checkout?" or "How do I run PHPUnit's own test suite?" This article provides the answers to these questions.
The git checkout is as easy as cloning the latest version (at the time of this post, it's 3.5). If you want a different version, you can checkout that branch with one or two more commands. The checkout comes with the test runner PHP script that is used when the "phpunit" command is run based on the "phpunit.xml.dist" file included in the checkout.