How to tell at runtime whether an iOS app is running through a TestFlight Beta install

Hi,

Due to the fact that TestFlight version will stop working after 30 days (entitlements expiration) we want to inform the beta users with an alert inside the app.

I know that people recommended the next code:

NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
NSString *receiptURLString = [receiptURL path];
BOOL isRunningTestFlightBeta = ([receiptURLString rangeOfString:@"sandboxReceipt"].location != NSNotFound);

But when I try it on the simulator I get

/Library/Developer/CoreSimulator/Devices/817FCA39-2A4E-4E44-A1A7-56344A31C3A5/data/Containers/Data/Application/E8229057-06B8-4786-BD07-7AE1697E85DE/StoreKit/receipt

When all say I should receive sandboxReceipt.

Is there some kind of a solution I can trust?

Thanks.