def test_registerChecker(self):
        checker = checkers.SSHProtocolChecker()
        self.assertEqual(checker.credentialInterfaces, [])
        checker.registerChecker(checkers.SSHPublicKeyDatabase(), )
        self.assertEqual(checker.credentialInterfaces, [ISSHPrivateKey])
        self.assertIsInstance(checker.checkers[ISSHPrivateKey],
                              checkers.SSHPublicKeyDatabase)
L{SSHProcotolChecker.registerChecker} should add the given checker to
dataset/ETHPy150Open twisted/twisted/twisted/conch/test/test_checkers.py/SSHProtocolCheckerTests.test_registerChecker