This class is skipped when looking for the source of an assertion.
When displaying which function an assert comes from, it's not too useful to see "backdropWebTestCase->backdropLogin()', we would like to see the test that called it. So we need to skip the classes defining these helper methods.
modules/ simpletest/ backdrop_web_test_case.php, line 94
- Base class for Backdrop tests.
protected $skipClasses = array(__CLASS__ => TRUE);