def test_add_header_resource(self):
        """
        When --add-header is specified, the resource is a composition that adds
        headers.
        """
        options = Options()
        options.parseOptions(
            ['--add-header', 'K1: V1', '--add-header', 'K2: V2']
        )
        service = makeService(options)
        resource = service.services[0].factory.resource
        self.assertIsInstance(resource, _AddHeadersResource)
        self.assertEqual(resource._headers, [('K1', 'V1'), ('K2', 'V2')])
        self.assertIsInstance(resource._originalResource, demo.Test)

        When --add-header is specified, the resource is a composition that adds
        headers.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_tap.py