[Mail] Test assertion for attachments as streams or raw content

[flozdra]

Hello,

The documentation states : The assertions only work with file-based attachments and not for streams or raw content.

Can I use the email.message.nodeMailerMessage.attachments variable to check attachments safely?
For example:

mails.assertSent(VerifyEmailNotification, (email) => {
  assert.notEmpty(email.message.nodeMailerMessage.attachments)
  return true
})

If so, why isn't it mentioned in the documentation?

Thanks!