def test_readline(self):
        """
        Calling L{_InputStream.readline} with no argument returns one line from
        the input stream.
        """
        bytes = b"hello\nworld"
        d = self._renderAndReturnReaderResult(
            lambda input: input.readline(), bytes)
        d.addCallback(self.assertEqual, b"hello\n")
        return d

        Calling L{_InputStream.readline} with no argument returns one line from
        the input stream.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_wsgi.py