On the CodeUtopia blog there's a recent post with info on creating a custom event listener in PHPUnit that can help keep you database data completely clean.

When testing code which uses the database, you would usually want to make sure the database stays pristine for each test - All tables should be empty, as any extra data could interfere with the tests. You could probably write an extended Testcase class which automatically does this before each test in setUp and afterwards in tearDown, but it may have some issues. [...] Luckily, PHPUnit has a way to add event listener that react to certain events.

It uses the TestListener interface to make the event handler that (with the help of Doctrine) starts up, makes the tables with data and wipes them out at the end.

Code for the sample listener is in the post and included is the method for checking to see if you even need to use the database or not.