Testing in-app purchase before submitting for review

is this even possible?
i am using unibill plugin and whenever i initiate purchae, i get “can’t find the product” error message from storekit.
I created in-app purchase product on iTunes connect and it shows as ‘ready to submit’ but as far as i know, i have to submit it with my game which needs its in-app purchase functionality tested!
it seems to be a chicken and egg problem.

@superp have you created a test user in iTunes Connect? You’ll need that to test the IAP in a sandbox environment (i.e. before submitting).