test_tools.py — langchain Source File

Source Code

"""Test Middleware handling of tools in agents."""

from collections.abc import Callable
from typing import Any

import pytest
from langchain_core.messages import HumanMessage, ToolMessage
from langchain_core.tools import tool
from langchain_core.tools.base import BaseTool
from langgraph.prebuilt.tool_node import ToolNode

from langchain.agents.factory import create_agent
from langchain.agents.middleware.types import (
    AgentMiddleware,
    AgentState,
    ModelCallResult,
    ModelRequest,
    ModelResponse,
)
from tests.unit_tests.agents.model import FakeToolCallingModel


def test_model_request_tools_are_base_tools() -> None:
    """Test that ModelRequest.tools contains BaseTool objects."""
    captured_requests: list[ModelRequest] = []

    @tool
    def search_tool(query: str) -> str:
        """Search for information."""
        return f"Results for: {query}"

    @tool
    def calculator(expression: str) -> str:
        """Calculate a mathematical expression."""
        return f"Result: {expression}"

    class RequestCapturingMiddleware(AgentMiddleware):
        def wrap_model_call(
            self,
            request: ModelRequest,
            handler: Callable[[ModelRequest], ModelResponse],
        ) -> ModelCallResult:
            captured_requests.append(request)
            return handler(request)

    agent = create_agent(
        model=FakeToolCallingModel(),
        tools=[search_tool, calculator],
        system_prompt="You are a helpful assistant.",
        middleware=[RequestCapturingMiddleware()],
    )

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

    # Verify that at least one request was captured
    assert len(captured_requests) > 0

    # Check that tools in the request are BaseTool objects
    request = captured_requests[0]
    assert isinstance(request.tools, list)
// ... (319 more lines)