test_summarization_middleware_binary_search_edge_cases() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/implementations/test_summarization.py lines 753–780

def test_summarization_middleware_binary_search_edge_cases() -> None:
    """Test binary search in _find_token_based_cutoff with edge cases."""
    middleware = SummarizationMiddleware(
        model=MockChatModel(), trigger=("messages", 5), keep=("tokens", 100)
    )

    # Test with single message that's too large
    def token_counter_single_large(messages: Iterable[MessageLikeRepresentation]) -> int:
        return len(list(messages)) * 200

    middleware.token_counter = token_counter_single_large

    single_message: list[AnyMessage] = [HumanMessage(content="x" * 200)]
    cutoff = middleware._find_token_based_cutoff(single_message)
    assert cutoff == 0

    # Test with empty messages
    cutoff = middleware._find_token_based_cutoff([])
    assert cutoff == 0

    # Test when all messages fit within token budget
    def token_counter_small(messages: Iterable[MessageLikeRepresentation]) -> int:
        return len(list(messages)) * 10

    middleware.token_counter = token_counter_small
    messages: list[AnyMessage] = [HumanMessage(content=str(i)) for i in range(5)]
    cutoff = middleware._find_token_based_cutoff(messages)
    assert cutoff == 0