test_tool_runtime_type_hints() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/test_injected_runtime_create_agent.py lines 512–543

def test_tool_runtime_type_hints() -> None:
    """Test that ToolRuntime provides access to state fields."""
    typed_runtime = {}

    # Use ToolRuntime without generic type hints to avoid forward reference issues
    @tool
    def typed_runtime_tool(x: int, runtime: ToolRuntime) -> str:
        """Tool with runtime access."""
        # Access state dict - verify we can access standard state fields
        typed_runtime["message_count"] = len(runtime.state.get("messages", []))
        return f"Typed: {x}"

    agent = create_agent(
        model=FakeToolCallingModel(
            tool_calls=[
                [{"args": {"x": 3}, "id": "typed_call", "name": "typed_runtime_tool"}],
                [],
            ]
        ),
        tools=[typed_runtime_tool],
        system_prompt="You are a helpful assistant.",
    )

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

    # Verify typed runtime worked -
    # should see 2 messages (HumanMessage + AIMessage) before tool executes
    assert typed_runtime["message_count"] == 2

    tool_message = result["messages"][2]
    assert isinstance(tool_message, ToolMessage)
    assert tool_message.content == "Typed: 3"