public function listGroupsCommand()
    {
        $groups = $this->cacheService->getValidCacheGroups();
        sort($groups);

        switch (count($groups)) {
            case 0:
                $this->outputLine('No cache groups are registered.');
                break;
            case 1:
                $this->outputLine('The following cache group is registered: "' . implode('", "', $groups) . '".');
                break;
            default:
                $this->outputLine('The following cache groups are registered: "' . implode('", "', $groups) . '".');
                break;
        }
    }