How to test pricing plan on a published app before making changes?

[sarik_matat]

We have an app that is Free to Install and already published on the app store. (LIVE_APP)
We also have a clone of this app that is connected to our dev environment for testing before deploying changes to live app. (DEV_APP)

Now we want to add a new pricing plan that offers some more features to the client. 

Before changing the pricing plan on our LIVE_APP, we want to first simulate it on our DEV_APP so we can make the necessary changes, test it and push the code to live after everything is built as necessary. But it seems there is no way to setup pricing plans on our DEV_APP without publishing it to the app store first. 

Does anyone know what we can do in this situation? How can I implement and test billing API before changing the pricing structure of the app?