Since crossing the gap to enter the cathedral is the first step in taking the Test of the Starstone, and the Test reconfigures itself for each person taking it - there shouldn't be any sort of floorplan, NPCs who visit (other than those who enter once, to die/vanish when they fail the test), etc.
You may want to take a look at:
http://pathfinder.wikia.com/wiki/Starstone_Cathedral
For what it's worth, I don't see any mentions in the newly-released Occult Mysteries. The best source material is probably Mythic Realms, although it's more about how to use the Test of the Starstone as a source of power for PCs using the Mythic rules, not really any info on the Cathedral itself.