'L{CommandDispatcher.ampBoxReceived} should locate the appropriate
command in its responder lookup, based on the \'_ask\' key.'

def test_receivedAsk(self):

    received = []
    def thunk(box):
        received.append(box)
        return amp.Box({'hello': 'goodbye'})
    input = amp.Box(_command='hello', _ask='test-command-id', hello='world')
    self.locator.commands['hello'] = thunk
    self.dispatcher.ampBoxReceived(input)
    self.assertEqual(received, [input])
