After trying to get code coverage reports and unit testing with PHPUnit and XDebug to work, Matthew Weir O'Phinney succeeded and got the reports running. Fortunately, he's shared how he's done it and an example of how to run the report.
I've been playing with PHPUnit a lot of late, particularly with framework development. One thing that's always hard to determine is how well your code is exercised -- basically, how much of the code is tested in the unit tests?
He gives an "executive summary" of how to get XDebug working and playing nice with PHPUnit as well as something a bit more detailed, following his experience with getting things up and running.