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

<?php

namespace SilverStripe\CMS\Tests\Model;

use SilverStripe\Core\Extension;
use SilverStripe\Dev\TestOnly;

class RedirectorPageTest_RedirectExtension extends Extension implements TestOnly
{
    public function onBeforeInit()
    {
        $this->owner->redirect('/foo');
    }
}