How does AngularJS dependency injection work with controller testing? - angularjs

Question

I'm trying to write tests for some AngularJS code, but can't even get a hello world to run. Suppose my code looks like this:
var myApp = angular.module("myApp", [])
myApp.controller("MyCtrl", function ($scope) {
$scope.hello = "world"
})
Then the angular docs here suggest that something like this (using jasmine) should work:
describe("my controller", function () {
it("should say hello", function () {
var $scope
inject(function ($rootScope, $controller) {
$scope = $rootScope.$new()
$controller('MyCtrl', {$scope: $scope})
})
expect($scope.hello).toBe("world")
}
}
Unfortunately, inject does not exist, and there are no hints in the docs as to where to get it. Thus the approach in the docs doesn't work.
Looking slightly farther afield, we find $injector, which can be created by angular.injector. From those docs, it's fairly clear that inject(f) should be $injector.invoke(f). So we stick this at the top of our code and make the change:
$injector = angular.injector(["myApp"])
Unfortunately, this gives the error "Uncaught Error: Unknown provider: $controllerProvider from myApp", which my google-fu seems unable to elucidate.
I had been using this ($injector) previously when I was only testing services, and it works perfectly. It is only when mixed with a controller definition that I get the error. It can handle the controller definition, or the $injector, but not both. To me this suggests some kind of priority conflict or double-initialization, but I can't figure it out.
So what does the "Unknown provider..." error mean, and how do I get my hello world controller test working? If someone can help sort me out, that would be great.

Answer 1

I created for you an skeleton you could use for that concrete controller.
describe('my controller', function() {
var $scope;
beforeEach(module('app'));
beforeEach(inject(function($rootScope, $controller) {
$scope = $rootScope.$new();
$controller('MyCtrl', { $scope: $scope });
}));
it('should contain world', function() {
expect($scope.hello).toBe('world');
});
});
Before each test, you inject your app module and before each test, you creates a new scope and instantiates your controller. Then you just need to write as much tests as you need.
We create a new scope in every tests to have a fresh state. We don't want to modify some $scope in one test and then have another one failing because you modified your $scope earlier.
Plunker: http://plnkr.co/edit/4hHqdsvnVwyUhiezpdhW?p=preview
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