Migrating to WordPress

We are completely redesigning our site and it will be hosted on WordPress. I would like to get all the 301s set up before we “throw the switch”. Instead of using the domain:
http://www.mysite.com/oldurl.html 301 to http://www.mysite.com/newdescriptiveurl/even-more-descriptive/

I would like to remove the domain so that the 301 won’t actually work until we throw the switch:
/oldurl.html 301 to /newdescriptiveurl/even-more-descriptive/

Will that work? Or do I need to wait until the new site is live and use the full URL?

https://wordpress.org/plugins/eps-301-redirects/