Depending on how your site is setup, you should be able to view it all before it becomes active. If you desperatly need a domain to try it with, you could consider first signing up with a username.lunarpages.com/ address and then moving over to the domain.
You will be able to access your website using another address before it becomes active. For example, my URL before my DNS moves over is:
http://galaxy.lunargpages.com/~username/I can view the entire site through there, as I upload it.
Another option is to use a 3rd party direction service for a temporary domain.
No-Ip Is one that I have used in the past.
Hope that helps!
- Ed :-)