'``wire_decode`` will not decode classes that are not in
``SERIALIZABLE_CLASSES``.'

def test_no_arbitrary_decoding(self):

    class Temp(PClass, ):
        'A    class.'
    SERIALIZABLE_CLASSES.append(Temp)
    def cleanup():
        if (Temp in SERIALIZABLE_CLASSES):
            SERIALIZABLE_CLASSES.remove(Temp)
    self.addCleanup(cleanup)
    data = wire_encode(Temp())
    SERIALIZABLE_CLASSES.remove(Temp)
    self.assertFalse(isinstance(wire_decode(data), Temp))
