def test_unmodified(self):
        """
        If a request is made with an I{If-Modified-Since} header value with a
        timestamp indicating a time after the last modification of the request
        resource, a 304 response is returned along with an empty response body
        and no Content-Type header if the application does not set one.
        """
        for line in [b"GET / HTTP/1.1",
                     b"If-Modified-Since: " + http.datetimeToString(100), b""]:
            self.channel.dataReceived(line + b'\r\n')
        result = self.transport.getvalue()
        self.assertEqual(httpCode(result), http.NOT_MODIFIED)
        self.assertEqual(httpBody(result), b"")
        # Since there SHOULD NOT (RFC 2616, section 10.3.5) be any
        # entity-headers, the Content-Type is not set if the application does
        # not explicitly set it.
        self.assertEqual(httpHeader(result, b"Content-Type"), None)

        If a request is made with an I{If-Modified-Since} header value with a
        timestamp indicating a time after the last modification of the request
        resource, a 304 response is returned along with an empty response body
        and no Content-Type header if the application does not set one.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_web.py