Better way to mock class attribute in python unit test

base.Base.assignment is simply replaced with a Mock object. You made it a descriptor by adding a __get__ method.

It's a little verbose and a little unnecessary; you could simply set base.Base.assignment directly:

def test_empty(self):    Base.assignment = {}    assert len(Base().assignment.values()) == 0

This isn't too safe when using test concurrency, of course.

To use a PropertyMock, I'd use:

with patch('base.Base.assignment', new_callable=PropertyMock) as a:    a.return_value = {'a': 1}

or even:

with patch('base.Base.assignment', new_callable=PropertyMock,            return_value={'a': 1}):

Perhaps I'm missing something, but isn't this possible without using PropertyMock?

with mock.patch.object(Base, 'assignment', {'bucket': 'head'}):   # do stuff

To improve readability you can use the @patch decorator:

from mock import patchfrom unittest import TestCasefrom base import Baseclass MyTest(TestCase):    @patch('base.Base.assignment')    def test_empty(self, mock_assignment):        # The `mock_assignment` is a MagicMock instance,        # you can do whatever you want to it.        mock_assignment.__get__.return_value = {}        self.assertEqual(len(Base().assignment.values()), 0)        # ... and so on

You can find more details at http://www.voidspace.org.uk/python/mock/patch.html#mock.patch.