I'm still having this issue on Xcode 26.6. I deleted and reinstalled the latest simulator runtime available ("iOS 26.5.1 + iOS 26.5 Simulator" / SDK version 26.5.1 (23F81a) / Simulator version 26.5 (23F77)), relaunched Simulator.app and created a fresh simulator.
For me, the issue also happens when tests are launched from Xcode directly. The workaround of launching the app manually and then launching the tests does not work, even though the Configuration.storekit file is in place in the filesystem hierarchy. Many methods on SKTestSession result in errors like
[SKTestSession] Error saving configuration file: Error Domain=SKInternalErrorDomain Code=3 "(null)"
or
[SKTestSession] Error deleting all transactions: Error Domain=SKInternalErrorDomain Code=3 "(null)"
or
Failed to purchase com.mycompany.product.id in off-device buy mode: Unable to Complete Request
My tests were legacy scheme-based tests; I converted them to test plans which made no difference.
I have submitted FB23721564 with these details.
Topic:
Developer Tools & Services
SubTopic:
Xcode
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