test_decorator_request_modification() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call.py lines 1348–1376

    def test_decorator_request_modification(self) -> None:
        """Test decorator modifying request before execution."""
        modified_prompts = []

        @wrap_model_call
        def add_system_prompt(
            request: ModelRequest,
            handler: Callable[[ModelRequest], ModelResponse],
        ) -> ModelCallResult:
            # Modify request to add system prompt
            modified_request = ModelRequest(
                messages=request.messages,
                model=request.model,
                system_prompt="You are a helpful assistant",
                tool_choice=request.tool_choice,
                tools=request.tools,
                response_format=request.response_format,
                state=AgentState[Any](messages=[]),
                runtime=None,
            )
            modified_prompts.append(modified_request.system_prompt)
            return handler(modified_request)

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

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

        assert modified_prompts == ["You are a helpful assistant"]