def testCredentials(self):
    self.assertTrue(self.cred_instance.Authenticate(u'sharrell', 'test'))
    cred_string = self.cred_instance.GetCredentials(u'sharrell', 'test',
                                                    self.core_instance)
    self.assertEqual(self.cred_instance.CheckCredential(cred_string,
                                                        u'sharrell',
                                                       self.core_instance),
                     u'')
    self.assertEqual(self.cred_instance.CheckCredential(u'test', u'sharrell',
                                                        self.core_instance),
                     None)