Testing on iPhone/iPad

The next version of my game app uses In App Purchase and Game Center so people can play each other rather than just play against the device.
To do this I have to sign out of my personal Apple ID on the devices and sign in with the Apple ID of one of my registered testers.
In the past I would build app, use Xcode to load it on my personal iPhone and iPad for testing between the devices. With latest iOS version it seems my registered testers’ Apple ID’s don’t work.
Do I have to use Test Flight to test now?