Worth pointing out: The test file names are required to end in "Test" (eg, MyTest.php) in order for the "Run Selenium Tests" to actually run the tests.
I installed PHPUnit 3.7, it appears to cause backwards compatibility issues with this module. When I try to Debug now, I get a message in the output saying "More than two positional arguments provided."
This module worked great for me until I upgraded from 3.6. I'll update if I find a work around or a fix is posted.