silverstripe-framework/tests/php/Forms/UploadFieldTest/ExtendedFile.php

<?php

namespace SilverStripe\Forms\Tests\UploadFieldTest;

use SilverStripe\Assets\File;
use SilverStripe\Dev\TestOnly;

/**
 * Used for testing the create-on-upload
 */
class ExtendedFile extends File implements TestOnly
{

    private static $has_many = array(
        'HasOneExtendedRecords' => 'UploadFieldTest_Record.HasOneExtendedFile'
    );
}