Here's the message I'm getting;

Please make changes below and resubmit for review. We were able to successfully publish this action and see that all of the criteria for built-in watch actions were present and functioning. Before we move forward with the approval process we will need you to provide a testing environment that provides an experience that a real user would experience. This staging environment should replicate the unique UI of your site Once you have made these changes, re-submit your action.

Isn't the actual application on a production environment without traffic coming in a valid testing environment?

I didn't see anywhere to specify a testing environment?

Were the FB testers aware that this application will be running inside a page tab? If you browse to the app directly it will look fairly unstyled, but still - FB should have no remit on creative preference, right? ;)