Hello @flying_kites.
You can install the plugin on a test site without any issue for most features – just make sure the Organization ID is set correctly under MembershipWorks > Plugin Settings. The only exceptions would be the member/event widgets – the links for the widgets are based on the URLs set under MembershipWorks > Organization Settings > Website Integration, so they may not link correctly on a test site. When you do go live with the new site you can update the URLs at that time (note: the URL settings will affect the live site, so do not update them until you’re ready to go live with changes).