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

<?php

namespace SilverStripe\CMS\Tests\Model;

use SilverStripe\Dev\TestOnly;
use Page;

class SiteTreeTest_ClassA extends Page implements TestOnly
{
    private static $table_name = 'SiteTreeTest_ClassA';

    private static $need_permission = [
        'ADMIN',
        'CMS_ACCESS_CMSMain'
    ];

    private static $allowed_children = [
        SiteTreeTest_ClassB::class
    ];
}