Mocking private methods in python

gistfile1.py

""" This is a simple gist to show how to mock
private methods. I've got lots of questions
regarding this topic. Most people seems confused.

Hope it helps.
"""


import unittest
import mock


class Car:
    def __private(self):
        return 1

    def no_private(self):
        return self.__private()


class CarTest(unittest.TestCase):

    def test_exception_raises(self):
        c = Car()
        with self.assertRaises(AttributeError):
            c.__private()

    def test_car_works(self):
        c = Car()
        self.assertEqual(c.no_private(), 1)

    def test_mock_private(self):
        c = Car()
        with mock.patch.object(c, '_Car__private', return_value=3) as method:
            c.no_private()
            method.assert_called_once_with()

if __name__ == "__main__":
    unittest.main()

@damorosodaragona use this:

from mock import patch, PropertyMock
with mock.patch.object(c, '_Car __private_attribute', new_callable=PropertyMock) as mock:
    mock.return_value = 4. # the value of the attr