def test_buffer(self):
        """
        Test a lot of different POP3 commands in an extremely pipelined
        scenario.

        This test may cover legitimate behavior, but the intent and
        granularity are not very good.  It would likely be an improvement to
        split it into a number of smaller, more focused tests.
        """
        return self.runTest(
            [b"APOP moshez dummy",
             b"LIST",
             b"UIDL",
             b"RETR 1",
             b"RETR 2",
             b"DELE 1",
             b"RETR 1",
             b"QUIT"],
            [b'+OK <moshez>',
             b'+OK Authentication succeeded',
             b'+OK 1',
             b'1 44',
             b'.',
             b'+OK ',
             b'1 0',
             b'.',
             b'+OK 44',
             b'From: moshe',
             b'To: moshe',
             b'',
             b'How are you, friend?',
             b'.',
             b'-ERR Bad message number argument',
             b'+OK ',
             b'-ERR message deleted',
             b'+OK '])

        Test a lot of different POP3 commands in an extremely pipelined
        scenario.

        This test may cover legitimate behavior, but the intent and
        granularity are not very good.  It would likely be an improvement to
        split it into a number of smaller, more focused tests.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_pop3.py