When they announce a new product they usually produce a mock-up cover for it, with recycled art from a previously published product before the actual cover is approved. That's all this is; if you follow the thread that Ironwolf linked they eventually mention it.
This is my feeling also. The sense I get is that the test is supposed to be different for each individual because even in game the details could be leaked out by those few who failed, yet survived. But I would not be opposed to seeing a successfully completed Test of the Starstone in print...
Agreed. One of the biggest reasons I've been buying into the recent DUNGEON Campaign Arcs (including the Shackled City hardcover) is for the lore that's inserted into every adventure.