Method modified_send

tests/test_routing.py:806–809

(msg: Message)

        scope["add_headers_middleware"] = True

        async def modified_send(msg: Message) -> None:
            if msg["type"] == "http.response.start":
                msg["headers"].append((b"X-Test", b"Set by middleware"))
            await send(msg)

        await self.app(scope, receive, modified_send)