Using QUnit and sinon.spy, how can I access my spy within an async callback?

Question

I am new to QUnit and sinon.js and working to build tests for an ember-cli package. I am having problems getting sinon.spy(Ember.run, 'later') to work with the code below. inside the callback Ember.run.later is not being spied / has no .getCalls() etc...

How can I handle this type of test?

test('#authenticate rejects with invalid credentials', function() {
  sinon.spy(Ember.run, 'later');

  var jwt = JWT.create(),
    expiresAt = (new Date()).getTime() + 60000;

  var token = {};
  token[jwt.identificationField] = 'test@test.com';
  token[jwt.tokenExpireName] = expiresAt;

  token = window.btoa(JSON.stringify(token));

  var credentials = {
    identification: 'username',
    password: 'password'
  };

  App.server.respondWith('POST', jwt.serverTokenEndpoint, [
    400,
    {
      'Content-Type': 'application/json'
    },
    '{"message":["Unable to login with provided credentials."]}'
  ]); 

  Ember.run(function(){
    App.authenticator.authenticate(credentials).then(null, function(){
      // Check that Ember.run.later was not called.
      equal(Ember.run.later.getCall(0), null);
    });
  });
  Ember.run.later.restore();
});

PS I currently am able to get this working by moving the sinon.spy and corresponding Ember.run.later.restore() to the module.setup() and module.teardown() methods respectively. Is there anything wrong with that that strategy other than it means they are spied for every test in my suite?

Thanks!

EDIT: Here is my authenticate method:

  authenticate: function(credentials) {
    var _this = this;
    return new Ember.RSVP.Promise(function(resolve, reject) {
      var data = _this.getAuthenticateData(credentials);
      _this.makeRequest(_this.serverTokenEndpoint, data).then(function(response) {
        Ember.run(function() {
          var tokenData = _this.getTokenData(response),
              expiresAt = tokenData[_this.tokenExpireName];
          _this.scheduleAccessTokenRefresh(expiresAt, response.token);          
          response = Ember.merge(response, { expiresAt: expiresAt });
          resolve(_this.getResponseData(response));
        });
      }, function(xhr) {
        Ember.run(function() {
          reject(xhr.responseJSON || xhr.responseText);
        });
      });
    });
  },