def test_receiveTwoNetstrings(self):
        """
        A stream of two netstrings can be received in two portions,
        where the first portion contains the complete first netstring
        and the length specification of the second netstring.
        """
        self.netstringReceiver.dataReceived(b"1:a,1")
        self.assertTrue(self.netstringReceiver._payloadComplete())
        self.assertEqual(self.netstringReceiver.received, [b"a"])
        self.netstringReceiver.dataReceived(b":b,")
        self.assertEqual(self.netstringReceiver.received, [b"a", b"b"])

        A stream of two netstrings can be received in two portions,
        where the first portion contains the complete first netstring
        and the length specification of the second netstring.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/test/test_basic.py