'L{MemCacheProtocol.checkAndSet} passes an additional cas identifier
that the server handles to check if the data has to be updated.'

def test_checkAndSet(self):

    return self._test(self.proto.checkAndSet('foo', 'bar', cas='1234'), 'cas    foo    0    0    3    1234\r\nbar\r\n', 'STORED\r\n', True)
