'Given TLSSNI01 and HTTP01 with appropriate combos.'

def test_common_case(self):

    challbs = (acme_util.TLSSNI01_P, acme_util.HTTP01_P)
    prefs = [challenges.TLSSNI01, challenges.HTTP01]
    combos = ((0,), (1,))
    self.assertEqual(self._call(challbs, prefs, combos), (0,))
    self.assertTrue(self._call(challbs, prefs, None))
    self.assertEqual(self._call(challbs[::(-1)], prefs, combos), (1,))
    self.assertTrue(self._call(challbs[::(-1)], prefs, None))
