Because the sandbox environment doesn’t have a subscription management UI like the production App Store, you’ll need to expose buttons or other means within the app to test purchases that trigger upgrades, downgrades, and cross grades.
I’m a bit confused on what to do to test a crossgrade. I have two plans, same level, different duration (annual and monthly). When I test in sandbox switching from monthly to annual, in Customer History I see the renewal events of the monthly one, then the change of renewal preference to annual, but then it stops renewing on either plan. On my I app I end up as if I just cancelled and not subscribed again.
Is this expected from the limitations as quoted above? If so, is there anything I can do to test this further or is that enough to assume it will work in production?