It seems that the can.Observe sort plugin doesn't handle triggering add events, which makes it pretty useless. This wasn't caught because the expected number of passed tests was never specified.
The correct number of passing tests has been added in commit 4aad9d7, but now needs to be resolved.
That sort plugin needs some serious fixing up #170 and #88 are probably related as well and should be fixed all together.
Trigger add event for sorted lists. Closes #170, closes #205