AcMailer\Options\MessageOptions::setAttachments PHP Method

    public function setAttachments($attachments)
    {
        if (is_array($attachments)) {
            $this->attachments = new AttachmentsOptions($attachments);
        } elseif ($attachments instanceof AttachmentsOptions) {
            $this->attachments = $attachments;
        } else {
            throw new InvalidArgumentException(sprintf('Attachments should be an array or an AcMailer\\Options\\AttachmentsOptions, %s provided', is_object($attachments) ? get_class($attachments) : gettype($attachments)));
        }
        return $this;
    }

 /**
  * @expectedException \AcMailer\Exception\InvalidArgumentException
  */
 public function testInvalidAttachmentsThrowException()
 {
     $this->messageOptions->setAttachments('foo');
 }