conftest.py

from unittest import mock
import pytest

sentinel = object()


@pytest.fixture()
def patching(monkeypatch, request):
    """Monkeypath.setattr shortcut.

    Example:
        .. code-block:: python

        def test_foo(patching):
            # execv value here will be mock.MagicMock by default.
            execv = patching('os.execv')

            patching('sys.platform', 'darwin')  # set concrete value
            patching.setenv('DJANGO_SETTINGS_MODULE', 'x.settings')

            # val will be of type mock.MagicMock by default
            val = patching.setitem('path.to.dict', 'KEY')
    """
    return _patching(monkeypatch, request)


class _patching(object):

    def __init__(self, monkeypatch, request):
        self.monkeypatch = monkeypatch
        self.request = request

    def __getattr__(self, name):
        return getattr(self.monkeypatch, name)

    def __call__(self, path, value=sentinel, name=None,
                 new=mock.MagicMock, **kwargs):
        value = self._value_or_mock(value, new, name, path, **kwargs)
        self.monkeypatch.setattr(path, value)
        return value

    def _value_or_mock(self, value, new, name, path, **kwargs):
        if value is sentinel:
            value = new(name=name or path.rpartition('.')[2])
        for k, v in kwargs.items():
            setattr(value, k, v)
        return value

    def setattr(self, target, name=sentinel, value=sentinel, **kwargs):
        # alias to __call__ with the interface of pytest.monkeypatch.setattr
        if value is sentinel:
            value, name = name, None
        return self(target, value, name=name)

    def setitem(self, dic, name, value=sentinel, new=mock.MagicMock, **kwargs):
        # same as pytest.monkeypatch.setattr but default value is MagicMock
        value = self._value_or_mock(value, new, name, dic, **kwargs)
        self.monkeypatch.setitem(dic, name, value)
        return value