public function testAttachContent()
{
$message = new Message();
$fileName = 'test.txt';
$fileContent = 'Test attachment content';
$message->attachContent($fileContent, ['fileName' => $fileName]);
$attachments = $message->getAttachments();
$this->assertCount(1, $attachments);
$attachment = $attachments[0];
$this->assertEquals($attachment['name'], $fileName);
$this->assertEquals($attachment['data'], base64_encode($fileContent));
$message->attachContent($fileContent);
$attachments = $message->getAttachments();
$this->assertCount(2, $attachments);
$attachment = $attachments[1];
$this->assertEquals($attachment['name'], 'file_1');
}