Breaking out functionally to a Rails Engine

Hey Upcasers,

Looking to break out a subscription process for a Huge Rails app. Looking for some guidance on how to do this, my question is about TDD and structure.

So I’m unsure how to handle the User model in the dummy app for tests. If I were to leave the base user model in the app using FactoryGirl what is the best way to do this?

In the engine I can use the Apps::Model, however currently the App is using devise and stripe but the more I think about this I should not only move stripe over but devise as well. Then the app’s models would just extend the engines’s, right?

This Engine is not going to be released as a gem however it should still be develop as it will be.

-Chris / Chewy