Testing releases
For some of the classes there are phpunit tests available since version 1.2.0. Check out the /test folder and the Readme included with the test suite. This framework only covers a few of the many functions right now and is by no means complete.
Manual testing
For testing phpCAS clients there small manual framework that was created for testing of new releases. It requires that you have phpCAS in your PATH and only requires one central configuration for all testcases.
It's basically most of the examples plus one interesting french ajax example that was posted a while back on the mailing list. The current testing process is pretty much clicking through all examples and then throw it out into some small deployments i have.