On the test.ical.ly blog there's a recent post that looks at a unit testing best practice for checking your Symfony (1.4) application's functionality.

Actually when I started this blog I was determined to use symfonys own lime unit test implementation because it is integrated and documented within the symfony documentation. But the more I worked with it the more I was put off by it. [...] PHPUnit on the other hand is the de facto standard for PHP. It is object oriented as well as well documented and maintained and it is fully xUnit compliant thus can easily be integrated into your continuous integration workflow.

He talks about the bootstrap for the testing, loading the configuration from a fixture and writing some test cases. He gives an example of a basic one and shows how it can fit into a test suite and includes some recommendations of how to test and what to test.