silverstripe-cms/tests/php/Model/SiteTreeTest_ExtensionA.php

<?php

namespace SilverStripe\CMS\Tests\Model;

use SilverStripe\CMS\Model\SiteTreeExtension;
use SilverStripe\Control\Controller;
use SilverStripe\Dev\TestOnly;

class SiteTreeTest_ExtensionA extends SiteTreeExtension implements TestOnly
{
    public static $can_publish = true;

    public function canPublish($member)
    {
        return static::$can_publish;
    }

    public function updateLink(&$link, $action = null)
    {
        $link = Controller::join_links($link, '?extra=1');
    }
}