test_wrap_tool_call_three_levels_composition() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_tool_call.py lines 494–555

def test_wrap_tool_call_three_levels_composition() -> None:
    """Test composition with three wrap_tool_call middleware levels."""
    call_log = []

    @wrap_tool_call(name="OuterWrapper")
    def outer(
        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(name="MiddleWrapper")
    def middle(
        request: ToolCallRequest, handler: Callable[[ToolCallRequest], ToolMessage | Command[Any]]
    ) -> ToolMessage | Command[Any]:
        call_log.append("middle_before")
        response = handler(request)
        call_log.append("middle_after")
        return response

    @wrap_tool_call(name="InnerWrapper")
    def inner(
        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")],
            [],
        ]
    )

    agent = create_agent(
        model=model,
        tools=[search],
        middleware=[outer, middle, inner],
        checkpointer=InMemorySaver(),
    )

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

    # Verify correct nesting order
    assert call_log == [
        "outer_before",
        "middle_before",
        "inner_before",
        "inner_after",
        "middle_after",
        "outer_after",
    ]

    tool_messages = [m for m in result["messages"] if isinstance(m, ToolMessage)]
    assert len(tool_messages) == 1