CustomEsmtpTransport example

$t = new EsmtpTransport('example.com', 0, false);
        $this->assertEquals('smtp://example.com', (string) $t);

        $t = new EsmtpTransport('example.com', 466, true);
        $this->assertEquals('smtps://example.com:466', (string) $t);
    }

    public function testExtensibility()
    {
        $stream = new DummyStream();
        $transport = new CustomEsmtpTransport(stream: $stream);

        $message = new Email();
        $message->from('sender@example.org');
        $message->addTo('recipient@example.org');
        $message->text('.');

        $transport->send($message);

        $this->assertContains("MAIL FROM:<sender@example.org> RET=HDRS\r\n", $stream->getCommands());
        $this->assertContains("RCPT TO:<recipient@example.org> NOTIFY=FAILURE\r\n", $stream->getCommands());
    }