This is a sequel to the original Extracting Domain Objects screencast. Once again, we'll look at Destroy All Software's catalog logic, pulling it out of the Django View (equivalent to a Rails controller), and moving it into its own domain-relevant class. Then we'll isolate and simplify the tests for both the view and the new Catalog class. Finally, we'll use the newly isolated tests to extend the behavior of the Catalog without changing or breaking the view and its tests.