test_logging_middleware() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call.py lines 58–79

    def test_logging_middleware(self) -> None:
        """Test middleware that logs calls without modification."""
        call_log = []

        class LoggingMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelCallResult:
                call_log.append("before")
                result = handler(request)
                call_log.append("after")
                return result

        model = GenericFakeChatModel(messages=iter([AIMessage(content="Response")]))
        agent = create_agent(model=model, middleware=[LoggingMiddleware()])

        result = agent.invoke({"messages": [HumanMessage("Test")]})

        assert call_log == ["before", "after"]
        assert result["messages"][1].content == "Response"