Verification steps:

Build and deploy UPS server from a PR.
Open Android application project that is using aerogear:aerogear-android-push 3.0.0+ (you can use unified-push-helloworld)
Set correct values in /app/src/main/assets/push-config.json file
Add registration to categories (in unified-push-helloworld it should be after this line)

.addCategory("WhatEver_123")

.addCategory("One.More")

Start an app on your device.
After successful registration of your device, verify that it was also registered to topic (same as categories):
curl -H "Authorization:key=GOOGLE_API_KEY" https://iid.googleapis.com/iid/info/ DEVICE_INSTANCE_ID ?details=true
Remove one or more categories from Android application code and run it on the same device again.
Verify that device was unsubscribed from the categories that you deleted (you can use same curl call).