How to simulate billing issue for a subscription in StoreKit Test?

To test the billing issue scenario in StoreKitTest environment, I set the Time Rate to 1 second to 1 day for 1 year subscription, then select SKErrorUnknown for Fail Transactions. But the subscription kept auto renewing, adding new transaction for the original transaction every 7 minutes.
It seems that Faile Transactions only works for user interaction purpose.
Is there a way to manually stop the auto renew in StoreKit Test environment, or sandbox?
How to simulate billing issue for a subscription in StoreKit Test?
 
 
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