How to test a real purchase on production?

When using TestFlight:

"All in-app purchases are free during the testing period." (https://developer.apple.com/testflight/testers/)


So, How can I test a real purchase on production before App is in AppStore?


just to clarify..

My App is already in the app store available to download with the In-App available to purchase.

I'm trying to upload a new app version and trying to perform a real purchase sanity test on the new version.

How to test a real purchase on production?
 
 
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