MessengerTransportListener example

use Symfony\Component\Mailer\Event\MessageEvent;
use Symfony\Component\Mailer\EventListener\MessengerTransportListener;
use Symfony\Component\Messenger\Stamp\TransportNamesStamp;
use Symfony\Component\Mime\Address;
use Symfony\Component\Mime\Header\Headers;
use Symfony\Component\Mime\Message;

class MessengerTransportListenerTest extends TestCase
{
    public function testNoMessengerTransportStampsByDefault()
    {
        $l = new MessengerTransportListener();
        $envelope = new Envelope(new Address('sender@example.com'), [new Address('recipient@example.com')]);
        $message = new Message(new Headers());
        $event = new MessageEvent($message, $envelope, 'smtp', true);
        $l->onMessage($event);
        $this->assertEmpty($event->getStamps());
    }

    public function testMessengerTransportStampViaHeader()
    {
        $l = new MessengerTransportListener();
        $envelope = new Envelope(new Address('sender@example.com'), [new Address('recipient@example.com')]);