Build and test your product subscription app extension with the Developer Console
With the Developer Console, you no longer need to build your app extension in an isolated environment, you can now test your app extension with real store data in a local store environment. Any changes made to your local environment will render immediately, meaning you no longer need to publish your app to view your modifications.
You can also render both desktop and mobile testing environments.
Learn more about product subscription app extensions and the developer console.