silverstripe-framework/tests/php/Model/ModelDataTest/ViewableDataTextExtension.php

<?php

namespace SilverStripe\Model\Tests\ModelDataTest;

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

class ModelDataTestExtension extends Extension implements TestOnly
{
    private function privateMethodFromExtension(): string
    {
        return 'Private function';
    }

    protected function protectedMethodFromExtension(): string
    {
        return 'Protected function';
    }

    public function publicMethodFromExtension(): string
    {
        return 'Public function';
    }
}