'When an invalid response is set on the L{CramMD5Credentials} (one that
is not the hex digest of the challenge, encrypted with the user\'s shared
secret) and C{checkPassword} is called with the user\'s correct shared
secret, it will return L{False}.'

def test_wrongPassword(self):

    c = CramMD5Credentials()
    chal = c.getChallenge()
    c.response = hexlify(HMAC('thewrongsecret', chal).digest())
    self.assertFalse(c.checkPassword('secret'))
