'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.'

def test_unmodified(self):

    for line in ['GET    /    HTTP/1.1', ('If-Modified-Since:    ' + http.datetimeToString(100)), '']:
        self.channel.dataReceived((line + '\r\n'))
    result = self.transport.getvalue()
    self.assertEqual(httpCode(result), http.NOT_MODIFIED)
    self.assertEqual(httpBody(result), '')
    self.assertEqual(httpHeader(result, 'Content-Type'), None)
