'If no test id is provided, we need to limit the test runner
to the Djangoapps we want to test.  Otherwise, it will
run tests on all installed packages. We do this by
using a default test id.'

@property
def _default_test_id(self):

    default_test_id = '{system}/djangoapps/*    common/djangoapps/*    openedx/core/djangoapps/*    openedx/tests/*    openedx/core/lib/*'
    if (self.root in ('lms', 'cms')):
        default_test_id += '    {system}/lib/*'
    if (self.root == 'lms'):
        default_test_id += '    {system}/tests.py'
        default_test_id += '    openedx/core/djangolib/*'
        default_test_id += '    openedx/features'
    return default_test_id.format(system=self.root)
