I was wondering - we know that Siuan and Moiraine became friends as novices, and that they were lovers by the time we saw them as Accepted in NS. Do we know when that happened, exactly?
It seems weird that Siuan never showed up in Moiraine's test for the Shawl (at least, that we saw). You'd think they'd exploit any emotional weakness. Maybe it's one of those Tower conventions? A lot of the testing Aes Sedai would probably have had pillow-friends themselves.
I think the answer is probably the most basic one: we didn't see most of the scenarios used during the test for the shawl, so they might have had a few instances where they used Siuan in the tests.
I wonder if the Aes Sedai, not being psychologists or therapists, realize that this test might be traumatic and it's this non-stop day of emotional abuse that makes Aes Sedai look so serene.
ETA: This might be a neat way for the R. Jordan estate to create more stories. A 'prequel' series of Aes Sedai Tests. Non-stop action with your favorite Aes Sedai!