'sign/unsign should be reversible'

def test_sign_unsign(self):

    signer = signing.Signer(u'predictable-secret')
    examples = [u'q;wjmbk;wkmb', u'3098247529087', u'3098247:529:087:', u'jkw    osanteuh    ,rcuh    nthu    aou    oauh    ,ud    du', u'\u2019']
    if six.PY2:
        examples.append('a    byte    string')
    for example in examples:
        signed = signer.sign(example)
        self.assertIsInstance(signed, str)
        self.assertNotEqual(force_str(example), signed)
        self.assertEqual(example, signer.unsign(signed))
