Checking the service callback function in an AngularJS controller test

I have a Controller that utilizes a service with a callback function upon success.

Controller Function

itemCtrl.save = function () {
    ItemService.save({ username: SessionService.getUsername() }, itemCtrl.item, function (res) {
        $scope.$emit('UPDATE_ITEMS');
        $modalInstance.close(res);
    });
};

spec

it('should close the modal when save is successful', function () {
    spyOn(itemSrv, 'save').and.callFake(function () {
        deferred = q.defer();
        deferred.resolve();
        return deferred.promise;
    });
    spyOn(modalInst, 'close').and.callThrough();
    ItemCtrl.save();
    scope.$digest();
    expect(modalInst.close).toHaveBeenCalled();
});

When I execute this test in karma, it fails because the close function of the modalinstance is not invoked. I believe the issue lies in the spec description, as the functionality is functioning correctly in the application. I have a couple of queries regarding this:

  • Is this the optimal way to describe callbacks on service calls within a controller?
  • How should I format my specs when using callbacks?

-- EDIT --

I have modified my service calls to handle results as promises:

itemCtrl.save = function () {
    ItemService.save({ username: SessionService.getUsername() }, horas.trabajo).$promise.then(function (res) {
        $scope.$emit('UPDATE_ITEMS');
        $modalInstance.close(res);
    });
};

I am assuming my tests are failing because my service does not return a promise (it possesses a promise attribute which I'm utilizing to emit the event and close the modalInstance). However, I am still unsure of how to return a promise using ng-resource.

My solution was to return an object with a $promise attribute, containing the promise provided by q.

spec

it('should close the modal when save is successful', function () {
    spyOn(itemSrv, 'save').and.callFake(function () {
        deferred = q.defer();
        deferred.resolve();
        return {$promise: deferred.promise};
    });
    spyOn(modalInst, 'close').and.callThrough();
    ItemCtrl.save();
    scope.$digest();
    expect(modalInst.close).toHaveBeenCalled();
});

Answer №1

Understanding the distinction between promises and callbacks can be tricky, but here is a workaround for your current situation:

spyOn(itemSrv, 'save').and.callFake(function (params, callback) {
    callback({some: 'response'});
});

Callback

By providing a function, you can determine the outcome based on a specific condition.

Promise

With promises, you receive an object with a method (then) that executes the 1st parameter on success or the 2nd parameter on failure.

These are simplified explanations, as there is more depth to both concepts.

Consider updating the save method in your service to return a promise rather than relying on a callback.

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