The idea is to run the tests against Backbone's Model to verify these tests which test the the usage of a model in the same scenarios as backbone itself will be valid.
If we want the basic cases to work the same way as Backbone.Model, then the tests should succeed when using Backbone.Model and not just Backbone.NestedModel.
If the `model.js` tests fail for either Backbone.Model or Backbone.NestedModel, that means that in the basic usage, the two are not compatible.