Side effect for mocks on object attributes access.

property_mock_example.py

from unittest import TestCase
import mock
from django import models
from django.core.exceptions import ObjectDoesNotExist

class Foo(models.Model):
    # ...
    @property
    def has_pending_related(self):
        try:
            return self.related_field.is_pending
        except ObjectDoesNotExist:
            return False
        

class FooTestCase(TestCase):
    # ...
    @mock.patch(Foo, 'related_field', new_callable=mock.PropertyMock)
    def test_pending_related(self, related_field):
        related_field.side_effect = ObjectDoesNotExist
        foo = Foo()
        self.assertFalse(foo.has_pending_related)