test_two_handlers_basic_composition() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_composition.py lines 61–94

    def test_two_handlers_basic_composition(self) -> None:
        """Test basic composition of two handlers."""
        execution_order = []

        def outer(
            request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
        ) -> ModelResponse:
            execution_order.append("outer-before")
            result = handler(request)
            execution_order.append("outer-after")
            return result

        def inner(
            request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
        ) -> ModelResponse:
            execution_order.append("inner-before")
            result = handler(request)
            execution_order.append("inner-after")
            return result

        composed = _chain_model_call_handlers([outer, inner])
        assert composed is not None

        result = composed(create_test_request(), create_mock_base_handler())

        assert execution_order == [
            "outer-before",
            "inner-before",
            "inner-after",
            "outer-after",
        ]
        # Outermost result is always _ComposedExtendedModelResponse
        assert isinstance(result, _ComposedExtendedModelResponse)
        assert result.model_response.result[0].content == "test"