Injecting a mock into an AngularJS service

The way I look at it, there's no need to mock the services themselves. Simply mock the functions on the service. That way, you can have angular inject your real services as it does throughout the app. Then, mock the functions on the service as needed using Jasmine's spyOn function.

Now, if the service itself is a function, and not an object that you can use spyOn with, there's another way to go about it. I needed to do this, and found something that works pretty well for me. See How do you mock Angular service that is a function?

You can inject mocks into your service by using $provide.

If you have the following service with a dependency that has a method called getSomething:

angular.module('myModule', [])
  .factory('myService', function (myDependency) {
        return {
            useDependency: function () {
                return myDependency.getSomething();
            }
        };
  });

You can inject a mock version of myDependency as follows:

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

  var mockDependency;

  beforeEach(module('myModule'));

  beforeEach(function () {

      mockDependency = {
          getSomething: function () {
              return 'mockReturnValue';
          }
      };

      module(function ($provide) {
          $provide.value('myDependency', mockDependency);
      });

  });

  it('should return value from mock dependency', inject(function (myService) {
      expect(myService.useDependency()).toBe('mockReturnValue');
  }));

});

Note that because of the call to $provide.value you don't actually need to explicitly inject myDependency anywhere. It happens under the hood during the injection of myService. When setting up mockDependency here, it could just as easily be a spy.

Thanks to loyalBrown for the link to that great video.