test_chat_prompt_template_message_class_tuples_with_placeholder() — langchain Function Reference

Source Code

libs/core/tests/unit_tests/prompts/test_chat.py lines 461–481

def test_chat_prompt_template_message_class_tuples_with_placeholder() -> None:
    """Test message class tuples combined with MessagesPlaceholder."""
    template = ChatPromptTemplate.from_messages(
        [
            (SystemMessage, "You are a helpful assistant."),
            MessagesPlaceholder("history"),
            (HumanMessage, "{question}"),
        ]
    )

    messages = template.format_messages(
        history=[HumanMessage(content="Hi"), AIMessage(content="Hello!")],
        question="How are you?",
    )

    assert len(messages) == 4
    assert isinstance(messages[0], SystemMessage)
    assert isinstance(messages[1], HumanMessage)
    assert isinstance(messages[2], AIMessage)
    assert isinstance(messages[3], HumanMessage)
    assert messages[3].content == "How are you?"