Patch unbound method using unittest.mock

patch_unbound_method.py

"""Patch an unbound class method."""

from unittest import mock
import pytest


class MyClass():
    """Demo class."""

    @classmethod
    def my_method(self, arg: int = 0) -> int:
        """Return 0 when invoked without an argument."""
        return arg


def my_method_mock(self: MyClass, arg: int = 1) -> int:
    """Return 1 when invoked without an argument."""
    return arg


_my_method_patch = mock.patch.object(MyClass, "my_method", classmethod(my_method_mock))


def test_my_method() -> None:
    """Unit test for my_method function."""
    obj = MyClass()
    assert obj.my_method() == 0


@_my_method_patch
def test_my_method_mock() -> None:
    """Unit test for my_method_mock function."""
    obj = MyClass()
    assert obj.my_method() == 1