How can I test events in angular?

Question

I need to test that events get correctly emitted or broadcast, and trigger events manually.

What's the best way to do this?

Answer 1

If you're just needing some testing on event firing and catching, this is how I do it. For ensuring that a certain event gets fired ($emit-ed or $broadcast-ed), a spy is the way to go. You need a reference to the scope that will be calling the $emit or $broadcast, and then just to do something like this:

spyOn(scope, "$emit")
//run code to test
expect(scope.$emit).toHaveBeenCalledWith("MY_EVENT_ID", other, possible, args);

If you don't need or don't want to worry about the arguments that are passed with the $emit, you can put an $on on the $rootScope and set a flag to know the event was emitted. Something like this:

var eventEmitted = false;
$rootScope.$on("MY_EVENT_ID", function() {
   eventEmitted = true;
});
//run code to test
expect(eventEmitted).toBe(true);

For testing functionality that runs when an event is caught ($on), it's a little easier. Just get a $rootScope from the inject function and then send the desired event.

$rootScope.$broadcast("EVENT_TO_TEST", other, possible, args);
//expects for event here

Now, I imagine this event handling would be happening in a directive or a controller (or both) For setting up directive tests, see https://github.com/vojtajina/ng-directive-testing. For setting up controller tests, see https://github.com/angular/angular-phonecat/blob/master/test/unit/controllersSpec.js#L27

Hope this helps.