langchain/libs/core/tests/unit_tests/fake/memory.py

from typing import List

from langchain_core.chat_history import (
    BaseChatMessageHistory,
)
from langchain_core.messages import BaseMessage
from langchain_core.pydantic_v1 import BaseModel, Field


class ChatMessageHistory(BaseChatMessageHistory, BaseModel):
    """In memory implementation of chat message history.

    Stores messages in an in memory list.
    """

    messages: List[BaseMessage] = Field(default_factory=list)

    def add_message(self, message: BaseMessage) -> None:
        """Add a self-created message to the store"""
        self.messages.append(message)

    def clear(self) -> None:
        self.messages = []