'Tests shouldn\'t be discovered twice when discovering on overlapping paths.'

def test_duplicates_ignored(self):

    base_app = 'forms_tests'
    sub_app = 'forms_tests.field_tests'
    with self.modify_settings(INSTALLED_APPS={'append': sub_app}):
        single = DiscoverRunner().build_suite([base_app]).countTestCases()
        dups = DiscoverRunner().build_suite([base_app, sub_app]).countTestCases()
    self.assertEqual(single, dups)
