Q:

Can I use a real Apple ID for testing In-App Purchases while developing an app?

In other words, must I create "Test Users" accounts in iTunesConnect.apple.com in order for me or my testers to test my app's In-App Purchase with the "sandbox environment" fake App Store?
I have two scenarios:

App running locally on device attached via USB cable
Distributed to testers via TestFlightApp.com

A:

If your app is in sandbox mode, you need an iTunes test account to test the In-App purchases. Both scenarios you describe apply. If you try to use real accounts, it will just throw you an error.
The same occurs with Game Center accounts.

