'Migrates the given setting and checks whether it correctly converted
to an ordered list of stores within Mixed.'

def assertMigrated(self, old_setting):

    new_mixed_setting = convert_module_store_setting_if_needed(copy.deepcopy(old_setting))
    self.assertEqual(new_mixed_setting['default']['ENGINE'], 'xmodule.modulestore.mixed.MixedModuleStore')
    new_stores = get_mixed_stores(new_mixed_setting)
    self.assertIsInstance(new_stores, list)
    return (new_mixed_setting, new_stores[0])
