As the 2.1 patch on the PTR is coming to an end, we strongly recommend all addon authors to test out their files and make sure they are working on the Public Test Realms.
In our file compatibility listing, there is an added checkbox named "2.1.0 PTR" in which you should check off files that work with the PTR. When the patch gets pushed live, this version will be renamed to "2.1.0" indicating that the addons listed in it are in fact tested and work with the new game client.
This link shows you a listing of the addons which have been tried out and found compatible with the PTR client. There is also an easy-nav link for it on the left menu of the World of Warcraft portal.