silverstripe-cms/tests/controller/ContentControllerTest_PageController.php

<?php

use SilverStripe\Dev\TestOnly;

class ContentControllerTest_PageController extends PageController implements TestOnly
{

    private static $allowed_actions = array(
        'second_index'
    );

    public function index()
    {
        return $this->Title;
    }

    public function second_index()
    {
        return $this->index();
    }
}