How would you test the APNS feedback service in the sandbox? Or in other words, how do you force a device to be in the feedback?
If you delete your app from a device, all you have to do is attempt send a single notification to that device and the next time you connect to the feedback server it will return that device. It will then not return the device again until you try to send another notification to that device.
Also, if you send multiple notifications to a device between connections to the feedback server, the device will be returned for every notification that was dennied.