How can I test Broadcast event in AngularJS

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);