@classmethod
def _get_tests(cls):
    """Yield an extractor's test cases as (URL, RESULTS) tuples"""
    tests = cls.test
    if not tests:
        return
    if len(tests) == 2 and (not tests[1] or isinstance(tests[1], dict)):
        tests = tests,
    for test in tests:
        if isinstance(test, str):
            test = test, None
        yield test
