public function testIsMultipart() { $message = new Message(); $this->assertFalse($message->isMultipart()); $message->addAttachment(new StringAttachment([])); $this->assertTrue($message->isMultipart()); $message = new Message(); $message->setBodyText('text'); $this->assertFalse($message->isMultipart()); $message->setBodyHtml('html'); $this->assertTrue($message->isMultipart()); }