silverstripe-framework/tests/php/Control/ControllerTest/ContainerController.php

<?php

namespace SilverStripe\Control\Tests\ControllerTest;

use SilverStripe\Control\Controller;
use SilverStripe\Dev\TestOnly;

class ContainerController extends Controller implements TestOnly
{

	private static $allowed_actions = array(
		'subcontroller',
	);

	public function subcontroller()
	{
		return new SubController();
	}

}