TestEdgeCasesAndErrorHandling Class — langchain Architecture

Source Code

libs/langchain_v1/tests/unit_tests/agents/test_system_message.py lines 999–1063

class TestEdgeCasesAndErrorHandling:
    """Test edge cases and error handling for system messages."""

    @pytest.mark.parametrize(
        ("content", "expected_blocks", "expected_prompt"),
        [
            ("", 0, ""),
            (
                [
                    {"type": "text", "text": "Block 1"},
                    {"type": "text", "text": "Block 2"},
                    {"type": "text", "text": "Block 3"},
                ],
                3,
                None,
            ),
        ],
        ids=["empty_content", "multiple_blocks"],
    )
    def test_system_message_content_variations(
        self, content: str | list[str | dict[str, Any]], expected_blocks: int, expected_prompt: str
    ) -> None:
        """Test SystemMessage with various content variations."""
        system_message = SystemMessage(content=content)

        model = GenericFakeChatModel(messages=iter([AIMessage(content="response")]))
        request = ModelRequest(
            model=model,
            system_message=system_message,
            messages=[],
            tool_choice=None,
            tools=[],
            response_format=None,
            state=AgentState(messages=[]),
            runtime=Runtime(),
        )
        assert request.system_message is not None

        if isinstance(content, list):
            assert isinstance(request.system_message.content_blocks, list)
            assert len(request.system_message.content_blocks) == expected_blocks
        else:
            assert len(request.system_message.content_blocks) == expected_blocks
            assert request.system_prompt == expected_prompt

    def test_reset_system_prompt_to_none(self) -> None:
        """Test resetting system prompt to None."""
        base_message = SystemMessage(content="Original prompt")

        model = GenericFakeChatModel(messages=iter([AIMessage(content="response")]))
        request = ModelRequest(
            model=model,
            system_message=base_message,
            messages=[],
            tool_choice=None,
            tools=[],
            response_format=None,
            state=AgentState(messages=[]),
            runtime=Runtime(),
        )

        new_request = request.override(system_message=None)

        assert new_request.system_message is None
        assert new_request.system_prompt is None