Harrison/file chat history (#3198)

Co-authored-by: Young Lee <joybro201@gmail.com>

tests/unit_tests/memory/__init__.py

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+"""Unit tests for memory module"""

tests/unit_tests/memory/chat_message_histories/__init__.py

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+"""Unit tests for chat_message_history modules"""

tests/unit_tests/memory/chat_message_histories/test_file.py

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+import tempfile
+from pathlib import Path
+from typing import Generator
+
+import pytest
+
+from langchain.memory.chat_message_histories import FileChatMessageHistory
+from langchain.schema import AIMessage, HumanMessage
+
+
+@pytest.fixture
+def file_chat_message_history() -> Generator[FileChatMessageHistory, None, None]:
+    with tempfile.TemporaryDirectory() as temp_dir:
+        file_path = Path(temp_dir) / "test_chat_history.json"
+        file_chat_message_history = FileChatMessageHistory(str(file_path))
+        yield file_chat_message_history
+
+
+def test_add_messages(file_chat_message_history: FileChatMessageHistory) -> None:
+    file_chat_message_history.add_user_message("Hello!")
+    file_chat_message_history.add_ai_message("Hi there!")
+
+    messages = file_chat_message_history.messages
+    assert len(messages) == 2
+    assert isinstance(messages[0], HumanMessage)
+    assert isinstance(messages[1], AIMessage)
+    assert messages[0].content == "Hello!"
+    assert messages[1].content == "Hi there!"
+
+
+def test_clear_messages(file_chat_message_history: FileChatMessageHistory) -> None:
+    file_chat_message_history.add_user_message("Hello!")
+    file_chat_message_history.add_ai_message("Hi there!")
+
+    file_chat_message_history.clear()
+    messages = file_chat_message_history.messages
+    assert len(messages) == 0
+
+
+def test_multiple_sessions(file_chat_message_history: FileChatMessageHistory) -> None:
+    # First session
+    file_chat_message_history.add_user_message("Hello, AI!")
+    file_chat_message_history.add_ai_message("Hello, how can I help you?")
+    file_chat_message_history.add_user_message("Tell me a joke.")
+    file_chat_message_history.add_ai_message(
+        "Why did the chicken cross the road? To get to the other side!"
+    )
+
+    # Ensure the messages are added correctly in the first session
+    messages = file_chat_message_history.messages
+    assert len(messages) == 4
+    assert messages[0].content == "Hello, AI!"
+    assert messages[1].content == "Hello, how can I help you?"
+    assert messages[2].content == "Tell me a joke."
+    expected_content = "Why did the chicken cross the road? To get to the other side!"
+    assert messages[3].content == expected_content
+
+    # Second session (reinitialize FileChatMessageHistory)
+    file_path = file_chat_message_history.file_path
+    second_session_chat_message_history = FileChatMessageHistory(
+        file_path=str(file_path)
+    )
+
+    # Ensure the history is maintained in the second session
+    messages = second_session_chat_message_history.messages
+    assert len(messages) == 4
+    assert messages[0].content == "Hello, AI!"
+    assert messages[1].content == "Hello, how can I help you?"
+    assert messages[2].content == "Tell me a joke."
+    expected_content = "Why did the chicken cross the road? To get to the other side!"
+    assert messages[3].content == expected_content