Angular test - triggering event from root scope with $emit

I am trying to test a controller which is calling a service. When this service has finished its job it is dispatching an event off the root scope with $emit. I am trying to simulate this in my tests, but I am unable to get the event handler to run. Can anyone see what I am doing wrong?

This is a basic version of my tests:

Files = Mocks.Files;

beforeEach(inject(function($rootScope, $controller) {
    scope = $rootScope.$new();
    $controller("HelpController", { $scope: scope });   // inherit scope from parent

    rootScope = $rootScope.$new(); 
    rootScope.profile = {
        ....
    };

    $controller("HelpContentEditorController", {
        $scope: scope,
        $rootScope: rootScope
        Files: Files
    });

    scope.$apply();
}));

it("should save FileResource to API", function() {
        spyOn(Files, "saveFileAPI");
        scope.saveContent();
        scope.$apply();
        rootScope.$emit("allFilesUploaded", []);
        rootScope.$apply();

        expect(Files.saveFileAPI).toHaveBeenCalled();
    });

And then inside the controller I am testing

function saveContent() {
    var blob = new $window.Blob([JSON.stringify($scope.content)], {type: "text/json"});
    blob.name = "help.json";

    $rootScope.$on("allFilesUploaded", onFilesUploaded);
    Files.upload([blob]);
}

function onFilesUploaded(event, files) {
    Files.saveFileAPI(files[0], files[0].extensions[0]).then(function(data) {
        ...
    }, function (error) {
        ...
    });
}

The test runs without errors, but the onFilesUploaded method is never called, so it fails. I am not sure if it something to do with the way I am inheriting scope, etc but I have tried a few alternatives

Thanks!