I am trying to test the RevenueCat Promotionals feature in Sandbox mode. The documentation talks about this feature being useful for giving Beta users access, so I assumed it was possible to test it in the Sandbox. I have selected a specific App User Id and am in the Customer Profile screen with the 'Viewing sandbox data' switch active. The screen correctly shows me the test subscriptions and cancellations that I have done on Google Play. All good.
However, when I then try to grant an entitlement in the 'Promotionals' box, that entitlement gets created in the production screen, not the sandbox view.
Is this intended behavior and if so, what is the recommended method of testing this feature - I guess because it has no impact on the app store billing it is ok to only be allocating to production?
What you are describing sounds like the intended behavior. There is no sandbox environment in RevenueCat, just sandbox and production transactions. A single customer can have both a sandbox and production transaction associated with their ID.
The RevenueCat promotional transactions are not considered "sandbox", but they will still grant a customer access to an entitlement whether they're running a test or production version of your app.