assertConversion example

use Symfony\Component\Mime\MessageConverter;
use Symfony\Component\Mime\Part\DataPart;

class MessageConverterTest extends TestCase
{
    public function testToEmail()
    {
        $file = file_get_contents(__DIR__.'/Fixtures/mimetypes/test.gif');
        $email = (new Email())->from('fabien@symfony.com')->to('you@example.com');
        $this->assertSame($email, MessageConverter::toEmail($email));

        $this->assertConversion((clone $email)->text('text content'));
        $this->assertConversion((clone $email)->html('HTML content <img src="cid:test.jpg" />'));
        $this->assertConversion((clone $email)
            ->text('text content')
            ->html('HTML content <img src="cid:test.jpg" />')
        );
        $this->assertConversion((clone $email)
            ->text('text content')
            ->html('HTML content <img src="cid:test.jpg" />')
            ->addPart((new DataPart($file, 'test.jpg', 'image/gif'))->asInline())
        );
        $this->assertConversion((clone $email)