When an event occurs, we'll kick off a timer and will save state to disk on completion. For many tests we make some changes and _hope_ that a save event was initiated before we add an observer and wait for the event. We do random things which might or might not have any effect (see bug 618188) I really don't want to make the session restore API messy, but perhaps it would be good to expose this information so we could do something like: if (ss.hasPendingSave()) observe then do stuff else just do stuff Perhaps we can just do this as a new interface nsISessionStoreTestInfo or something so we can just QI. Or maybe it would make sense to just expose this sort of thing to nsISessionStore... Thoughts?