Testing transaction observer code
Verify that your app activates its payment transaction observer by using breakpoints.
Overview
Review the transaction observer’s implementation of the SKPaymentTransactionObserver protocol. Verify that the SKPaymentTransactionObserver listens for transactions when:
Your app isn’t displaying its store UI
If you didn’t recently initiate a purchase
Locate the call to the add(_:) method of SKPaymentQueue in your code. Verify that your app calls this method at app launch. For more information, see Setting up the transaction observer for the payment queue.