Hello!
I know this post is from some months back but wanted to comment here.
The answer to your question is, no. You cannot use or test a domain if it is not registered.
Would an option like Domain Tasting be of interest?
If so, Epik does offer that feature to customers. It means you register a domain (cannot be a cctld) and you chose to either keep the domain before day 5 or let it go. If you let it go, you are refunded to your In-Store Credit all but .25cents. So, you get pretty much four whole days to test out the domain.
If domain tasting is of interest to you, let me know and we can discuss the next steps to take. Have a wonderful day!