'Verify that setting the _expiration_date property does not set the explicit flag.'

def test_expiration_datetime_explicitly_set_to_none(self):

    (verified_mode, __) = self.create_mode('verified', 'Verified    Certificate', 10)
    self.assertFalse(verified_mode.expiration_datetime_is_explicit)
    verified_mode.expiration_datetime = None
    self.assertFalse(verified_mode.expiration_datetime_is_explicit)
    self.assertIsNone(verified_mode.expiration_datetime)
