Use standalone “mock” package#

Python 3 users might want to use a newest version of the mock package as published on PyPI than the one that comes with the Python distribution.

mock_use_standalone_module = true

This will force the plugin to import mock instead of the unittest.mock module bundled with Python 3.4+.

Improved reporting of mock call assertion errors#

This plugin monkeypatches the mock library to improve pytest output for failures of mock call assertions like Mock.assert_called_with() by hiding internal traceback entries from the mock module.

It also adds introspection information on differing call arguments when calling the helper methods. This features catches AssertionError raised in the method, and uses pytest’s own advanced assertions to return a better diff:

mocker = <pytest_mock.MockerFixture object at 0x0381E2D0>

    def test(mocker):
        m = mocker.Mock()
>       m.assert_called_once_with('', bar=4)
E       AssertionError: Expected call: mock('', bar=4)
E       Actual call: mock('fo')
E       pytest introspection follows:
E       Args:
E       assert ('fo',) == ('',)
E         At index 0 diff: 'fo' != ''
E         Use -v to get the full diff
E       Kwargs:
E       assert {} == {'bar': 4}
E         Right contains more items:
E         {'bar': 4}
E         Use -v to get the full diff AssertionError
========================== 1 failed in 0.03 seconds ===========================

This is useful when asserting mock calls with many/nested arguments and trying to quickly see the difference.

This feature is probably safe, but if you encounter any problems it can be disabled in your pytest.ini file:

mock_traceback_monkeypatch = false

Note that this feature is automatically disabled with the --tb=native option. The underlying mechanism used to suppress traceback entries from mock module does not work with that option anyway plus it generates confusing messages on Python 3.5 due to exception chaining