def test_consumeLength(self):
        """
        C{_consumeLength} returns the expected length of the
        netstring, including the trailing comma.
        """
        self.netstringReceiver._remainingData = b"12:"
        self.netstringReceiver._consumeLength()
        self.assertEqual(self.netstringReceiver._expectedPayloadSize, 13)

        C{_consumeLength} returns the expected length of the
        netstring, including the trailing comma.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/test/test_basic.py