Comment 5 for bug 1215946

Is it possible that the u/i is calling something other than CheckForUpdate() when using the --testing=no-update? That's the only method (and UpdateAvailableStatus is the only signal) that's supported by that testing mode. It will respond to other methods, but you should not count on it. This is true of all the testing modes; they only guarantee the behavior of the use cases defined on the wiki page: https://wiki.ubuntu.com/ImageBasedUpgrades/Client

If that's not the case, please paste the entire dbus dialog with the --testing=no-update server. I can't possibly see any other way this could be happening.