test_dynamic_prompt_uses_state() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_decorators.py lines 658–683

def test_dynamic_prompt_uses_state() -> None:
    """Test that dynamic_prompt can use state information."""

    @dynamic_prompt
    def custom_prompt(request: ModelRequest) -> str:
        msg_count = len(request.state["messages"])
        return f"Prompt with {msg_count} messages"

    # Verify it uses state correctly
    original_request = ModelRequest(
        model=FakeToolCallingModel(),
        system_prompt="Original",
        messages=[HumanMessage("Hello")],
        tool_choice=None,
        tools=[],
        response_format=None,
        state={"messages": [HumanMessage("Hello"), HumanMessage("World")]},
        runtime=None,
    )

    def mock_handler(req: ModelRequest) -> ModelResponse:
        return ModelResponse(result=[AIMessage(content=req.system_prompt)])

    result = custom_prompt.wrap_model_call(original_request, mock_handler)
    assert isinstance(result, ModelResponse)
    assert result.result[0].content == "Prompt with 2 messages"