def test_update_and_get_image_is_called(self): # holds all mock objects mocker = Controller() # mock object to be used in tested routine instead of real thing mocked_game_state = mocker.mock() # record exactly how mock object should be used in tested routine mocked_game_state.update() mocked_game_state.get_image((500, 500)) # prepare it for real use mocker.replay() # init states manager = GameStateManager() manager.state = "Mock" manager._states["Mock"] = mocked_game_state # call tested routine screen = manager.get_rendered_screen((500, 500)) # test if it was used right mocker.verify()