I have (possibly) good news. SKTestSession.failTransactionsEnabled has been depreacted since iOS17, but it behaves strangely on iOS17. (lldb) po session.failTransactionsEnabled false (lldb) po session.failTransactionsEnabled = false 0 elements (lldb) po session.failTransactionsEnabled true We may work around this issue by not setting a value for this variable. // before session.failTransactionsEnabled = false // after if #unavailable(iOS 17.0) { session.failTransactionsEnabled = false } In iOS17 we probably need to use simulatedError(forAPI:).