How to trigger $emit to test $on listener in a controller when testing it with Jasmine?

Question

I've got a controller and want to test it with a Jasmine. There is an $on listener in the scope of controller that I want to test. How do I trigger $emit event to run $on listener?

myApp.controller('superCtrl', function ($scope) {
    $scope.hero = 'Rafael ninja turtle';

    $scope.$on('change_hero', function (event, new_hero) {
        $scope.hero = new_hero;
    });
});

Test $on listener works proper when 'change_hero' event comes:

describe('Super controller', function () {
    var $scope,
        super_controller;

    beforeEach(function(){

        module('myApp');

        inject(function($rootScope, $controller){
            $scope = $rootScope.$new();

            super_controller = $controller('superCtrl', {$scope: $scope});

            spyOn($scope, '$on');
        });

    });

    it('should change change hero on change_hero event', function (){

        var new_hero = 'Ralf ninja turtle',
            sub_scope = $scope.$new();

        sub_scope.$emit('change_hero', new_hero);

        expect($scope.$on).toHaveBeenCalled();
        expect($scope.hero).toBe('Ralf ninja turtle');
    });

});

Answer 1

Looks like you need to call spyOn before creating the controller. Also, you should call andCallThrough() otherwise the real method won't be called and your test will fail