How to test Ember error substate, with Ember CLI test runner?

I've set up an error substate route/controller/template according to http://ift.tt/1XCIqT7. Manually browsing my app, I can trigger error conditions and get directed to the substate. Confirmed with Ember Inspector.

I'd like to automatically test the substate. However, Ember CLI's test runner fails any test when a route's model hook rejects. In other words, the test fails before I can navigate to the error substate.

How can I automatically test my error substate?

Ember: 2.2.0

Ember CLI: 1.13.13