Yes, it is great for testing. I think it has been added to a few testing announcements, although I’m not sure how many folks have actually tried it out.
The wiki post is the more digestible version of this much long winded/more elaborate post:
It’s not a new method by any means, I’ve been doing it for a while. But yes, for things like ISO testing, installing multiple desktop environments/multiple distros, pulling in a testing repo, or any kind of major tinkering where you don’t want to mess up your setup it is just great!