Sketch Business Logic and Define the Seam

Let’s create the service class that will hold our business logic. This will codify the contract between our code and the controller. We should be able to do this without breaking the system test. Once that’s done, we can then start to build out the real business logic.

We’ll call the service WidgetCreator, and it’ll go in app/services/ as widget_creator.rb. We’ll need to create the app/services directory. We’ll give it one method, create_widget, and it’ll accept a Widget instance initialized with the parameters received from the UI.