DAlterHooks.php

<?php

declare (strict_types=1);
namespace Drupal\ddd_hook_order_test\Hook;

use Drupal\Core\Hook\Attribute\Hook;

/**
 * This class contains hook implementations.
 *
 * By default, these will be called in module order, which is predictable due
 * to the alphabetical module names.
 */
class DAlterHooks {
    public function testAlter(array &$calls) : void {
        $calls[] = __METHOD__;
    }
    public function testSubtypeAlter(array &$calls) : void {
        $calls[] = __METHOD__;
    }

}