Test AngularJS service initialization

Question

I have an AngularJS service that loads data from localStorage while "initializing" (i.e. in the factory function), like this:

module.service('myService', function ($localStorage) {
    var data = $localStorage.data;
    if (!isValid(data)) // isValid omitted on purpose, not relevant.
      data = undefined;

    return {
      getData: function() {
        return data;
      }
      setData: function(value) {
        if (isValid(value))
          data = value;
      }
    };
}

In my tests, I'd like to check that data is actually loaded from localStorage if the value is present there and valid; this is not about testing isValid, but the service initialization that uses it and $localStorage.

I'd like to be able to call the myService factory inside my test. I'm getting an initialized instance of it in the beforeEach hook since I need to test methods of myService as well. I think I need to have a different instance created for my specific initialization test, but since services are singletons in AngularJS, I'm not sure whether this can be done.

describe('myService', function() {
  myService = $localStorage = null;

  beforeEach(module('app'));

  beforeEach(inject(function($injector) {
    myService = $injector.get('myService');
    $localStorage = $injector.get('$localStorage');
  });

  it('should look for stuff in localStorage on creation', function () {
    $localStorage.data = 'my data';
    // I'd like to call service factory here!!
    myService.getData().should.equal('my data');
  });
});

Can this be achieved? Does my code have a difficult-to-test structure, or am I disrespecting the "Angular way" and this should be done differently?

Answer 1

Try this:

describe('myService', function() {
  myService = $localStorage = null;

  beforeEach(module('app'));

  beforeEach(inject(function($injector) {
    $localStorage = $injector.get('$localStorage');
    $localStorage.data = 'my data';
    myService = $injector.get('myService');
  });

  it('should look for stuff in localStorage on creation', function () {
    myService.getData().should.equal('my data');
  });
});