def METHOD_NAME(self):
    sds_setting = self.test_app.settings_set.select_subclasses().get(
        name="primary_geoserver"
    )
    sds_setting.spatial_dataset_service = None
    sds_setting.save()
    self.assertRaises(
        TethysAppSettingNotAssigned,
        self.test_app.settings_set.select_subclasses()
        .get(name="primary_geoserver")
        .get_value,
    )