Best way to validate backup?

I have been running ZxBackup for a few weeks now, seems great!

But of course the proof will be in a recovery scenario...

So, what's the best way to validate the backup?

I can imagine two scenarios:

1. Recover a single mailbox account
2. Recover entire Server

My server is on a VM, so I was considering just making a clone of that, and whacking the /opt/zimbra folder and taking it from there...