langchain/tests/unit_tests/llms/fake_chat_model.py

"""Fake Chat Model wrapper for testing purposes."""
from typing import Any, List, Mapping, Optional

from langchain.callbacks.manager import (
    AsyncCallbackManagerForLLMRun,
    CallbackManagerForLLMRun,
)
from langchain.chat_models.base import SimpleChatModel
from langchain.schema import AIMessage, BaseMessage, ChatGeneration, ChatResult


class FakeChatModel(SimpleChatModel):
    """Fake Chat Model wrapper for testing purposes."""

    def _call(
        self,
        messages: List[BaseMessage],
        stop: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForLLMRun] = None,
    ) -> str:
        return "fake response"

    async def _agenerate(
        self,
        messages: List[BaseMessage],
        stop: Optional[List[str]] = None,
        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
    ) -> ChatResult:
        output_str = "fake response"
        message = AIMessage(content=output_str)
        generation = ChatGeneration(message=message)
        return ChatResult(generations=[generation])

    @property
    def _llm_type(self) -> str:
        return "fake-chat-model"

    @property
    def _identifying_params(self) -> Mapping[str, Any]:
        return {"key": "fake"}