Error: Timeout - Async callback was not invoked within timeout specified.... .DEFAULT_TIMEOUT_INTERVAL

I have an angular service class : -

angular.module('triggerTips')

.service('userData', function ($rootScope, $http, $log, $firebase) {

this._log = {
  service : 'userData'
};

// Synchronized objects storing the user data
var config;
var userState;

// Loads the user data from firebase
this.init = function(readyCallback) {
  var log = angular.extend({}, this._log);
  log.funct = 'init';

  var fireRef = new Firebase('http://ift.tt/1GOf4Vn' + $rootScope.clientName);
  config = $firebase(fireRef.child('config')).$asObject();
  userState = $firebase(fireRef.child('userState').child($rootScope.userName)).$asObject();

  Promise.all([config.$loaded(), userState.$loaded()]).
    then(
      function() {
        if(config == null || Object.keys(config).length < 4) {
          log.message = 'Invalid config';
          $log.error(log);
          return;
        }

        if(!userState.userProperties) {
          userState.userProperties = {};
        }

        if(!userState.contentProperties) {
          userState.contentProperties = {};
        } 

        log.message = 'User Properties: ' + JSON.stringify(userState.userProperties);
        $log.debug(log);

        log.message = 'Content Properties: ' + JSON.stringify(userState.contentProperties);
        $log.debug(log);

        log.message = 'Loaded user data from firebase';
        $log.debug(log);
        readyCallback();
      },
      function() {
        log.message = 'Unable to load user data from firebase';
        $log.error(log);
      }
    );
};

// Returns the initial tip configuration
this.getConfig = function() {
  return config;
};

// Set the value of a user property
// A user property is something about the user himself
this.setUserProperty = function(property, value) {
  if(!userState.userProperties) {
    userState.userProperties = {};
  }
  userState.userProperties[property] = value;
  userState.$save();
  $rootScope.$broadcast('user-property-change', property);
};

// Get the value of a user property
this.getUserProperty = function(property) {
  if(userState.userProperties) {
    return userState.userProperties[property];
  }
};

// Set the value of a user content property
// A content property is something about a particular peice of content for a particular user
this.setContentProperty = function(contentName, property, value) {
  if(!userState.contentProperties[contentName]) {
    userState.contentProperties[contentName] = {};
  }

  userState.contentProperties[contentName][property] = value;
  userState.$save();
  $rootScope.$broadcast('content-property-change', contentName, property);
};

// Increment a count property on the user state for a given tip
this.incrementContentProperty = function(contentName, property) {
  if(!userState.contentProperties[contentName]) {
    userState.contentProperties[contentName] = {};
  }
  if(!userState.contentProperties[contentName][property]) {
    userState.contentProperties[contentName][property] = 0;
  }

  userState.contentProperties[contentName][property]++;
  userState.$save();
  $rootScope.$broadcast('content-property-change', contentName, property);
};

// Returns the user state for a given tip and property
this.getContentProperty = function(contentName, property) {
  if(userState.contentProperties) {
    var t = userState.contentProperties[contentName];
    if(t) {
      return t[property];
    }
  }
};

});

I am trying to unit test this service using jasmine:-

my unit test is :-

    'use strict';

describe('Service: userData', function () {

  // load the service's module
  beforeEach(function() {
    module('triggerTips');
  });

  // instantiate service
  var userData;
  beforeEach(inject(function (_userData_) {
    userData = _userData_;
  }));

  it('should load correctly', function () {
    expect(!!userData).toBe(true);
  });

  describe('after being initialized', function () {

    beforeEach(function(done) {
      // Unable to get this working because the callback is never called
        userData.getConfig(function() {
            done();
        });
        jasmine.DEFAULT_TIMEOUT_INTERVAL = 2000;
    });

    it('should have a valid config', function (done) {
         setTimeout(function() {
             expect(Object.keys(userData.getConfig()).length == 0);
             done();
           }, 1500);}); }); });

I read about the Asynchronous Support in Jasmine, but as I am rather new to unit testing with javascript couldn't make it work.

I am receiving an error :

Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL

Can somebody help me providing working example of my code with some explanation?