Bug report

Bug description:

Thereset_mock(return_value=True) method behaves in a wrong/inconsistent way.
When used withMagicMock, the methodreset_mock(return_value=True) does not reset the return values of the magic methods. Only if you call for example__str__ and then call the reset_mock function, the return value will be reset, but not to the default value.

fromunittestimportmockmm=mock.MagicMock()print(type(mm.__str__()))mm.reset_mock(return_value=True)print(type(mm.__str__()))print(type(mm.__hash__()))mm.reset_mock(return_value=True)print(type(mm.__hash__()))

Output

<class'str'><class'unittest.mock.MagicMock'><class'int'><class'unittest.mock.MagicMock'>

Since Python 3.9PRreset_mock now also resets child mocks. This explains the behaviour. Calling the__str__ method creates a childMagicMock with a set return value. Since this child mock now exists, its return value is reset when reset_mock(return_value=True) is called.
Although this can be logically explained, it's counter-intuitive and annoying as I'm never sure which values are being reset.

I would expect the same behaviour asMock. The return value of__str__ and other magic methods should not be effected.

fromunittestimportmockm=mock.Mock()print(type(m.__str__()))m.reset_mock(return_value=True)print(type(m.__str__()))print(type(m.__hash__()))m.reset_mock(return_value=True)print(type(m.__hash__()))

Output

<class'str'><class'str'><class'int'><class'int'>

CPython versions tested on:

3.10

Operating systems tested on:

Linux

Linked PRs

• gh-123934: FixMagicMock not to reset magic method return values #124038
• [3.13] gh-123934: FixMagicMock not to reset magic method return values (GH-124038) #124231
• [3.12] gh-123934: FixMagicMock not to reset magic method return values (GH-124038) #124232