Ember - Return a promise from beforeModel not working with Qunit

In my ApplicationRoute I implement a beforeModel hook that does a server call to see if a valid session exists. If it does, then the app navigates to the 'dashboard' route, otherwise it goes to the 'login' route. I am trying to implement some tests and I can't seem to get it to work with QUnit. I keep getting:

Assertion failed: You have turned on testing mode, which disabled the run-loop's autorun. You will need to wrap any code with asynchronous side-effects in an Ember.run

Here is a plunker http://plnkr.co/edit/e0Q4qz?p=preview I have simulated a server call by creating a doLater method that returns a promise and executes a method in a few milliseconds. The only way I can get it to work is to not return a promise from the beforeModel hook. Am I using App.deferReadiness() and Ember.run() correctly?

App = Ember.Application.create({});

App.Router.map(function() {
  this.resource('dashboard');
  this.resource('login');
});

App.ApplicationRoute = Ember.Route.extend({
  alreadyChecked: false,

  beforeModel: function() {
    var route = this;

    // uncomment this line to stop this hook returning a promise
    // return route.transitionTo(localStorage.user ? 'dashboard' : 'login');

    if (!this.alreadyChecked) {
      return doLater(function() {
        // without the alreadyChecked flag, this function gets called twice
        route.set('alreadyChecked', false);
        route.transitionTo(localStorage.user ? 'dashboard' : 'login');
      });
    }
  }
});

App.LoginRoute = Ember.Route.extend({
  actions: {
    login: function() {
      var route = this;
      doLater(function() {
        localStorage.user = "Bill";
        route.transitionTo('dashboard');
      });
    }
  }
});

App.DashboardRoute = Ember.Route.extend({
  actions: {
    logout: function() {
      var route = this;
      doLater(function() {
        localStorage.user = "";
        route.transitionTo('login');
      });
    }
  }
});

function doLater(fn) {
  return Ember.RSVP.Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve(fn());
    }, 500);
  });
}


// run the tests
if (true) { // toggle this boolean to run the app in testing mode
  App.rootElement = '#ember-testing';
  App.setupForTesting();
  App.injectTestHelpers();

  module('integration tests', {
    setup: function() {
      Ember.run(function() {
        App.reset();
        localStorage.user = "";
        App.deferReadiness();
      });
    }
  });

  test('can navigate to login page', function() {
    expect(1);
    Ember.run(App, 'advanceReadiness');
    visit("/login").then(function() {
      ok(true, "Tests work");
    });
  });
}