The Room of Requirement is open on jkrowling.com, and inside you'll find the last W.O.M.B.A.T. test. This one was supposed to be harder, but I thought it was actually possibly easier. I hope I don't jinx my results by saying that!
The instructions to get to it are below, so don't click if you want to figure it out yourself.
Get to the main page of jkrowling.com (i.e. Jo's desk) and click the eraser. That should take you to a hallway facing the door. Wait for the fly to land on the window and then click it. It should turn into a key which you'll want to drag over and use to unlock the door. Once the door opens, move the circle to the bottom part of the line (it will sparkle) and then put the triangle on top of that (it will also sparkle). (It makes the symbol on the spine of Deathly Hallows--pictured above.) Click to open the test booklet, and you're on your way. Good luck!