'Test receiving a challenge message.'

def test_onChallenge(self):

    d = self.init.start()
    challenge = domish.Element((NS_XMPP_SASL, 'challenge'))
    challenge.addContent(u'bXkgY2hhbGxlbmdl')
    self.init.onChallenge(challenge)
    self.assertEqual('my    challenge', self.init.mechanism.challenge)
    self.init.onSuccess(None)
    return d
