def METHOD_NAME(self):
    """Tests that config versions of None are cleaned from stored data."""
    ### setup
    defaults = {"foo": "bar"}
    self.plugin.get_settings_defaults = mock.MagicMock()
    self.plugin.get_settings_defaults.return_value = defaults
    # stored config version is None
    in_config = {"_config_version": None, "foo": "fnord"}
    self.settings.get_all_data.return_value = in_config
    ### execute
    self.plugin.on_settings_cleanup()
    ### assert
    # minimal config without config version should have been set
    self.settings.set.assert_called_once_with([], {"foo": "fnord"})