How to test local functions within angular controllers? - angularjs

Question

Let's suppose I have a controller like:
angular
.module("app", [])
.controller("NewsFeedController", [
"$scope",
"NewsFeedService",
function ($scope, NewsFeedService) {
$scope.news = [
{ stamp: 1 },
{ stamp: 9 },
{ stamp: 0 }
];
$scope.onScroll = function () {
/*
might do some stuff like debouncing,
checking if there's news left to load,
check for user's role, whatever.
*/
var oldestStamp = getOldestNews().stamp;
NewsFeedService.getOlderThan(oldestStamp);
/* handle the request, append the result, ... */
};
function getOldestNews () {
/* code supposed to return the oldest news */
}
}
]);
getOldestNews is declared as a local function since there is no point to expose it in the $scope.
How should I deal with it? How can I actually test this function?
describe("NewsFeedController", function () {
beforeEach(module("app"));
var $controller, $scope, controller;
beforeEach(inject(function (_$controller_) {
$controller = _$controller_;
$scope = {};
controller = $controller("NewsFeedController", { $scope: $scope });
}));
it("should return the oldest news", function () {
// How do I test getOldestNews?
});
});
By the way, it'd be great if the solution also works for local functions within services and directives.
Related questions:
How can we test non-scope angular controller methods?
How do I mock local variable for a function in a service? Jasmine/Karma tests

Answer 1

Now I see what you really want to do in your code. I don't think it is necessary to test the private function, because it does not contain enough logic. I would suggest you only create a spy on the NewsFeedService to test that the correct data is send to that service.
describe("NewsFeedController", function () {
beforeEach(module("app"));
var $controller, $scope, controller;
var newsFeedServiceMock = jasmine.createSpyObj('NewsFeedService', ['getOlderThan']);
beforeEach(inject(function (_$controller_) {
$controller = _$controller_;
$scope = {};
controller = $controller("NewsFeedController", { $scope: $scope, NewsFeedService : newsFeedServiceMock });
}));
it("should return the oldest news", function () {
$scope.news = [
{ stamp: 76 },
{ stamp: 4 },
{ stamp: 83 }
];
$scope.onScroll();
expect(newsFeedServiceMock.getOlderThan).toHaveBeenCalledWith(83);
});
});
This way you can check if the correct behaviour is done by your onScroll method, without the need to check private methods. You only want to test the public methods, so you have flexibility when you want to create private methods to separate logic, without having to alter your tests.