Class MonkeyPatch

src/_pytest/monkeypatch.py:114–430

Helper to conveniently monkeypatch attributes/items/environment variables/syspath. Returned by the :fixture:`monkeypatch` fixture. .. versionchanged:: 6.2 Can now also be used directly as `pytest.MonkeyPatch()`, for when the fixture is not available. In this case, use

@final
class MonkeyPatch:
    """Helper to conveniently monkeypatch attributes/items/environment
    variables/syspath.

    Returned by the :fixture:`monkeypatch` fixture.

    .. versionchanged:: 6.2
        Can now also be used directly as `pytest.MonkeyPatch()`, for when
        the fixture is not available. In this case, use
        :meth:`with MonkeyPatch.context() as mp: <context>` or remember to call
        :meth:`undo` explicitly.
    """

    def __init__(self) -> None:
        self._setattr: list[tuple[object, str, object]] = []
        self._setitem: list[tuple[Mapping[Any, Any], object, object]] = []
        self._cwd: str | None = None
        self._savesyspath: list[str] | None = None

    @classmethod
    @contextmanager
    def context(cls) -> Generator[MonkeyPatch]:
        """Context manager that returns a new :class:`MonkeyPatch` object
        which undoes any patching done inside the ``with`` block upon exit.

        Example:

        .. code-block:: python

            import functools


            def test_partial(monkeypatch):
                with monkeypatch.context() as m:
                    m.setattr(functools, "partial", 3)

        Useful in situations where it is desired to undo some patches before the test ends,
        such as mocking ``stdlib`` functions that might break pytest itself if mocked (for examples
        of this see :issue:`3290`).
        """
        m = cls()
        try:
            yield m
        finally:
            m.undo()

    @overload
    def setattr(
        self,
        target: str,
        name: object,
        value: NotSetType = ...,
        raising: bool = ...,
    ) -> None: ...

    @overload
    def setattr(
        self,