How to mock AngularJS promises using Jasmine / Karma?

Question

This is my controller:

angular.module("AuthenticationApp", ["BaseApp"])
    .controller("AuthCtrl", ["$http", "BaseService", function($http, BaseService) {
        var self = this;

        BaseService.fetch.stuffs()
          .then(function(data) {
            self.stuffs = data;
        });

    }]);

This my BaseService (the factory I need to mock):

angular.module("BaseApp", ["ngRoute"])

    .factory("BaseService", ["$http", "$q", function($http, $q) {
        var self = this;

        self.fetch = {
         stuffs: function() {
           return $http.get("/api/stuffs/")
             .then(function(response) {
                 return response.data;
           });
         }
        };    

        return self;
    }]);

I have no idea where to start. What I tried was this:

describe('Controller: AuthCtrl', function() {
    var ctrl, mockBaseService;

    beforeEach(function() {

        mockBaseService = {
            stuffs: 'test',
            fetch: { 
                stuffs: function() {
                    return {
                      then: function() {
                          return {stuffs: "stuffs"};
                      },
                    }
                },
            },
        };

        spyOn(mockBaseService.fetch, 'stuffs');

        module('BaseApp', function($provide) {
            $provide.value('BaseService', mockBaseService);
        });

        module('AuthenticationApp');

        inject(function($controller) {
            ctrl = $controller('AuthCtrl', {
            });
        });
    });

    it('BaseService.fetch.stuffs should be called on page load', function() {
        expect(mockBaseService.fetch.stuffs).toHaveBeenCalled();
        expect(ctrl.stuffs).toBe({stuffs: "stuffs"});
    });

});

But when I test this code, I get an error saying:

TypeError: Cannot read property 'then' of undefined
    at new <anonymous> (/home/user/Documents/ebdjango/ebdjangoapp/static/js/home.js:15:11)

home.js line 15 is this line in the controller:

       return $http.get("/api/stuffs/")
         .then(function(response) { // line 15
             return response.data;
       });

How do I mock this correctly?

Edit: I read the documentation mentioned in the comments and and changed up mockBaseService to this:

describe('Controller: AuthCtrl', function() {
    var ctrl, mockBaseService;

    beforeEach(function() {
        // create promise
        var deferred = $q.defer();
        var promise = deferred.promise;
        // make promise.then return {stuffs: "stuffs"}
        promise.then(function(value) { return {stuffs: "stuffs" };  });

        mockBaseService = {
            stuffs: 'stuffs',
            fetch: { 
                stuffs: function() {
                    return promise;
                },
            },
        };

        spyOn(mockBaseService.fetch, 'stuffs');

        module('BaseApp', function($provide) {
            $provide.value('BaseService', mockBaseService);
        });

        module('AuthenticationApp');

        inject(function($controller) {
            ctrl = $controller('AuthCtrl', {
            });
        });
    });

    it('BaseService.fetch.stuffs should be called on page load', inject(function($rootScope) {
        deferred.resolve('test');
        $rootScope.$apply();
        expect(mockBaseService.fetch.stuffs).toHaveBeenCalled();
        expect(ctrl.stuffs).toBe({stuffs: "stuffs"});
    }));

});

But this returns a ReferenceError: $q is not defined error. I tried injecting _$q_ like so:

beforeEach(inject(function(_$q_) {
    $q = _$q_;
    // ... everything else goes here... //

But then I get an error saying Error: Injector already created, can not register a module!. Here: injector already created. can not register a module it says this issue can be solved if we do module('someApp') before inject($someDependency). But I can't do

module('BaseApp', function($provide) {
    $provide.value('BaseService', mockBaseService);
});

before injecting _$q_ since $q is used for mockBaseService. Where do I go from here?

Answer 1

to mock promises I always do

1) spyOn(service,'method').andCallFake( $q.when( Fixture.data() ) )

Do not create that mockBaseService, I've done that before and its a lot to write for nothing It's also possible to use AngularJS built in way of intercepting $http i.e

2) $httpBackend.when('GET', '/url').respond(Fixture.data())

I definitely prefer 1) as I like to isolate myself in a certain layer when doing testing. It comes down to a matter of taste I guess