'L{amp.Descriptor.fromBox} can interpret an L{amp.AmpBox} constructed by
L{amp.Descriptor.toBox} to reconstruct a file descriptor value.'

def test_roundTrip(self):

    name = 'alpha'
    nameAsBytes = name.encode('ascii')
    strings = {}
    descriptor = 17
    sendObjects = {name: descriptor}
    argument = amp.Descriptor()
    argument.toBox(nameAsBytes, strings, sendObjects.copy(), self.protocol)
    receiver = amp.BinaryBoxProtocol(amp.BoxDispatcher(amp.CommandLocator()))
    for event in self.transport._queue:
        getattr(receiver, event[0])(*event[1:])
    receiveObjects = {}
    argument.fromBox(nameAsBytes, strings.copy(), receiveObjects, receiver)
    self.assertEqual((descriptor + self.fuzz), receiveObjects[name])
