test_wrap_tool_call_multiple_middleware_composition() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_tool_call.py lines 372–417

def test_wrap_tool_call_multiple_middleware_composition() -> None:
    """Test multiple wrap_tool_call middleware compose correctly."""
    call_log = []

    @wrap_tool_call
    def outer_middleware(
        request: ToolCallRequest, handler: Callable[[ToolCallRequest], ToolMessage | Command[Any]]
    ) -> ToolMessage | Command[Any]:
        call_log.append("outer_before")
        response = handler(request)
        call_log.append("outer_after")
        return response

    @wrap_tool_call
    def inner_middleware(
        request: ToolCallRequest, handler: Callable[[ToolCallRequest], ToolMessage | Command[Any]]
    ) -> ToolMessage | Command[Any]:
        call_log.append("inner_before")
        response = handler(request)
        call_log.append("inner_after")
        return response

    model = FakeToolCallingModel(
        tool_calls=[
            [ToolCall(name="search", args={"query": "test"}, id="1")],
            [],
        ]
    )

    # First middleware in list is outermost
    agent = create_agent(
        model=model,
        tools=[search],
        middleware=[outer_middleware, inner_middleware],
        checkpointer=InMemorySaver(),
    )

    result = agent.invoke(
        {"messages": [HumanMessage("Search")]},
        {"configurable": {"thread_id": "test"}},
    )

    # Verify correct composition order
    assert call_log == ["outer_before", "inner_before", "inner_after", "outer_after"]
    tool_messages = [m for m in result["messages"] if isinstance(m, ToolMessage)]
    assert len(tool_messages) == 1