test_messages_placeholder() — langchain Function Reference

Architecture documentation for the test_messages_placeholder() function in test_chat.py from the langchain codebase.

Function python LangChainCore LanguageModelBase

Entity Profile

LangChainCore→ LanguageModelBase→ test_messages_placeholder() — langchain Function Reference

Dependency Diagram

graph TD
  70d45ff8_4b5a_da31_c021_ff572f67bccc["test_messages_placeholder()"]
  00c8bbe0_a31c_1ac8_487a_bfd5a9d6b117["test_chat.py"]
  70d45ff8_4b5a_da31_c021_ff572f67bccc -->|defined in| 00c8bbe0_a31c_1ac8_487a_bfd5a9d6b117
  style 70d45ff8_4b5a_da31_c021_ff572f67bccc fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/tests/unit_tests/prompts/test_chat.py lines 1045–1056

def test_messages_placeholder() -> None:
    prompt = MessagesPlaceholder("history")
    with pytest.raises(KeyError):
        prompt.format_messages()
    prompt = MessagesPlaceholder("history", optional=True)
    assert prompt.format_messages() == []
    assert prompt.format_messages(
        history=[("system", "You are an AI assistant."), "Hello!"]
    ) == [
        SystemMessage(content="You are an AI assistant."),
        HumanMessage(content="Hello!"),
    ]