python-repositories/tests/unit/context_aware_interface_test.py

"""Unit tests for ContextAwareInterface."""

from __future__ import annotations

import pytest

from python_repositories.interfaces.context_aware_interface import ContextAwareInterface


class FakeContextManager:
    """Plain class that satisfies ContextAwareInterface without inheritance."""

    def __enter__(self) -> FakeContextManager:
        return self

    def __exit__(
        self, exc_type: type | None, exc_val: object | None, exc_tb: object | None
    ) -> None:
        pass


def accepts_context_aware(context: ContextAwareInterface) -> None:
    """Type-checking hook for ContextAwareInterface structural subtyping."""
    with context:
        pass


def test_instantiation_fails_when_enter_not_implemented() -> None:
    """Test that instantiation fails if __enter__ is not implemented."""

    class Incomplete(ContextAwareInterface):
        """A class that does not implement __enter__."""

        def __exit__(
            self, exc_type: type | None, exc_val: object | None, exc_tb: object | None
        ) -> None:
            pass

    with pytest.raises(TypeError):
        _ = Incomplete()  # type: ignore


def test_instantiation_fails_when_exit_not_implemented() -> None:
    """Test that instantiation fails if __exit__ is not implemented."""

    class Incomplete(ContextAwareInterface):
        """A class that does not implement __exit__."""

        def __enter__(self) -> Incomplete:
            return self

    with pytest.raises(TypeError):
        _ = Incomplete()  # type: ignore


def test_structural_subtyping() -> None:
    """Test that a plain class satisfies ContextAwareInterface structurally."""
    context: ContextAwareInterface = FakeContextManager()
    accepts_context_aware(context)
    assert isinstance(context, ContextAwareInterface)