Ember QUnit test is failing. Don't know why


I’m updating my unit tests to use the new Ember-QUnit approach and I’m running into a problem with one computed property test.

I’m trying to test that hire_date returns the correct string, but the test keeps failing with undefined is not a function. I know the setup is correct because another test, location_class, works just fine.

Can anyone offer insight as to why this is failing?

TypeError: undefined is not a function
    at null.<anonymous> (
    at ComputedPropertyPrototype.get (
    at get (
    at Ember.Observable.Ember.Mixin.create.get (
    at Object.<anonymous> (
    at Object.wrapper (
    at Object.Test.run (
    at process (

Here’s a gist containing pertinent pieces of my code.