I implemented a User model with BackboneJS and RequireJS with test cases in Jasmine. How can I improve?

Question

I've been taking a stab at implementing test cases using the Jasmine testing framework. To do so, I've made an application which has a User object. This User object is created by the server, but its ID is stored in a couple of client-side data storage locations. When a new User model is initialized I check those storage locations before fetching User data from the server.

My model is doing too much work in the constructor. This is making it difficult to test. I am wondering how I could improve my architecture to make it easier to test and also if there are any other mistakes with how I am implementing Backbone, Require, and Jasmine. Thanks!

//  A singleton representing the sole logged on user for the program.
//  Tries to load itself by ID stored in localStorage and then by chrome.storage.sync.
//  If still unloaded, tells the server to create a new user and assumes that identiy.
define(['programState'], function(programState) {
    'use strict';
    var userIdKey = 'UserId';

    //  Loads user data by ID from the server, writes the ID
    //  to client-side storage locations for future loading and then announces
    //  that the user has been loaded fully.

    function fetchUser(shouldSetSyncStorage) {
        this.fetch({
            success: function(model) {
                //  TODO: Error handling for writing to sync too much.
                //  Write to sync as little as possible because it has restricted read/write limits per hour.
                if (shouldSetSyncStorage) {
                    chrome.storage.sync.set({ userIdKey: model.get('id') });
                }

                localStorage.setItem(userIdKey, model.get('id'));

                //  Announce that user has loaded so managers can use it to fetch data.
                model.trigger('loaded');
            },
            error: function (error) {
                console.error(error);
            }
        });
    }

    //  User data will be loaded either from cache or server.
    var User = Backbone.Model.extend({
        defaults: {
            id: localStorage.getItem(userIdKey),
            name: '' 
        },

        urlRoot: programState.getBaseUrl() + 'User/',

        //  TODO: I am doing too much work in this initialize constructor. 
        initialize: function () {
            //  If user's ID wasn't found in local storage, check sync because its a pc-shareable location, but doesn't work synchronously.
            if (this.isNew()) {
                var self = this;
                //  chrome.Storage.sync is cross-computer syncing with restricted read/write amounts.

                chrome.storage.sync.get(userIdKey, function (data) {
                    //  Look for a user id in sync, it might be undefined though.
                    var foundUserId = data[userIdKey];

                    if (typeof foundUserId === 'undefined') {

                        //  No stored ID found at any client storage spot. Create a new user and use the returned user object.
                        self.save({}, {

                            //  TODO: I might need to pull properties out of returned server data and manually push into model.
                            //  Currently only care about userId, name can't be updated.
                            success: function (model) {
                                //  Announce that user has loaded so managers can use it to fetch data.
                                self.trigger('loaded');
                            },
                            error: function(error) {
                                console.error(error);
                            }
                        });

                    } else {
                        //  Update the model's id to proper value and call fetch to retrieve all data from server.
                        self.set('id', foundUserId);
                        fetchUser.call(self, false);
                    }
                });

            } else {
                //  User's ID was found in localStorage. Load immediately.
                fetchUser.call(this, true);
            }
        }
    });

    //  Return an already instantiated User model so that we have only a single instance available.
    return new User();
});

and here is my sole test case currently with notes on the others:

//  Test cases for the background's user model. Hopes to ensure that the user
//  loads successfully from the server from a client-side id or, alternatively,
//  that it is created successfully by the server.
define(['user'], function (user) {
    'use strict';
    var userIdKey = 'UserId';

    describe('The User', function () {
        //  TODO: The way user is currently written isn't very testable.
        //  I would like to be able to test more specific actions such as the tests left blank here.

        xit('creates when no id found in storage locations', function () {
            localStorage.setItem(userIdKey, null);
        });

        xit('loads from chrome.sync if no id found in localStorage', function () {

        });

        xit('loads from localStorage', function() {

        });

        //  Makes sure a user loads. A bad test case because the user's loadability is dependent on code
        //  that isn't modifiable by this method, so I can only infer current state.
        it('loads', function () {
            var userLoaded = false;
            runs(function () {
                user.on('loaded', function () {
                    userLoaded = true;
                });
            });

            waitsFor(function() {
                return userLoaded === true;
            }, "The user should have loaded.", 5000);

            runs(function() {
                expect(user.isNew()).toBe(false);
            });
        });

    });
});