def test_readlineNegative(self):
        """
        Calling L{_InputStream.readline} with a negative integer as an argument
        returns one line from the input stream.
        """
        bytes = b"input stream line one\nline two"
        d = self._renderAndReturnReaderResult(
            lambda input: input.readline(-1), bytes)
        d.addCallback(self.assertEqual, b"input stream line one\n")
        return d

        Calling L{_InputStream.readline} with a negative integer as an argument
        returns one line from the input stream.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_wsgi.py