How can I test Broadcast event in AngularJS

Unit TestingAngularjs

Unit Testing Problem Overview


I have a controller which emits a broadcast event on the rootscope. I would like to test that the broacast event is fired correctly.

My code in my controller looks like this:

   $scope.$watch("pageIndex", function(){
    if($scope.pageIndex == 4)
    {
      // emit social share
      $rootScope.$broadcast('myEvent');
    }
  });

I have tried to test it with the following code:

	it('Should call myEvent when pageIndex is 4',function(){
	scope.pageIndex = 4;
	scope.$apply();
	expect(rootScope.$on).toHaveBeenCalledWith('myEvent');
});

But it tells me that the code isn't called, which I have manually tested that it does. I have then tried with the following code:

it('Should call myEvent when pageIndex is 4',function(){
	var listener = jasmine.createSpy('listener');
	rootScope.$on('myEvent', listener);
	scope.pageIndex = 4;
	scope.$apply();
	expect(listener).toHaveBeenCalled();
});

But with the same negative result. Is there a way to test that an event is broadcasted?

Unit Testing Solutions


Solution 1 - Unit Testing

Assuming you're using Jasmine, the following is working great for me.

... other unit test setup code ...

var rootScope;
beforeEach(inject(function($injector) {
    rootScope = $injector.get('$rootScope');
    spyOn(rootScope, '$broadcast');
}));

describe("my tests", function() {
    it("should broadcast something", function() {
        expect(rootScope.$broadcast).toHaveBeenCalledWith('myEvent');
    });
});

If you're broadcasting a message and attaching objects to it, you can even test that the objects match expectations

someObj = { ... something ... };
expect(rootScope.$broadcast).toHaveBeenCalledWith('someEvent', someObj);

Solution 2 - Unit Testing

Here's how its done with mochaJs, with sinon for mocks and chai for expectations.

describe("broadcast test", function() {
  beforeEach(inject(function($rootScope){
   sinon.spy($rootScope, "$broadcast")
   scope.foo() //this broadcasts the event. $rootScope.$broadcast("testEvent")
 }))

it("broadcasts the event", inject(function($rootScope){
 expect($rootScope.$broadcast.calledWith("testEvent")).to.be.true
}))

})

Attributions

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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionDofsView Question on Stackoverflow
Solution 1 - Unit TestingMike PughView Answer on Stackoverflow
Solution 2 - Unit TestingSudhir NView Answer on Stackoverflow