AngularJS Promise Callback Not Trigged in JasmineJS Test

Question

Problem Intro I'm trying to unit test an AngularJS service that wraps the Facebook JavaScript SDK `FB` object; however, the test isn't working, and I haven't been able to figure out why. Also, the service code does work when I run it in a browser instead of a JasmineJS unit test, run with Karma test runner. I'm testing an asynchronous method using Angular promises via the `$q` object. I have the tests set up to run asynchronously using the Jasmine 1.3.1 async testing methods, but the `waitsFor()` function never returns `true` (see test code below), it just times-out after 5 seconds. (Karma doesn't ship with the Jasmine 2.0 async testing API yet). I think it might be because the `then()` method of the promise is never triggered (I've got a `console.log()` set up to show that), even though I'm calling `$scope.$apply()` when the asynchronous method returns, to let Angular know that it should run a digest cycle and trigger the `then()` callback...but I could be wrong. This is the error ou…

Accepted Answer

TL;DR

Call `$rootScope.$digest()` from your test code and it'll pass:

```
it('should return false if user is not logged into Facebook', function () {
  ...

var userLoggedIn;

inject(function (Facebook, $rootScope) {
    Facebook.getUserLoginStatus($rootScope).then(function (data) {
      console.log("Found data!");
      userLoggedIn = data;
    });

$rootScope.$digest(); // <-- This will resolve the promise created above
    expect(userLoggedIn).toEqual(false);
  });
});
```

Plunker here.

Note: I removed `run()` and `wait()` calls because they're not needed here (no actual async calls being performed).

Long explanation

Here's what's happening: When you call `getUserLoginStatus()`, it internally runs `FB.getLoginStatus()` which in turn executes its callback immediately, as it should, since you've mocked it to do precisely that. But your `$scope.$apply()` call is within that callback, so it gets executed before the `.then()` statement in the test. And since `then()` creates a new promise, a new digest is required for that promise to get resolved.

I believe this problem doesn't happen in the browser because of one out of two reasons:

- `FB.getLoginStatus()` doesn't invoke its callback immediately so any `then()` calls run first; or

- Something else in the application triggers a new digest cycle.

So, to wrap it up, if you create a promise within a test, explicitly or not, you'll have to trigger a digest cycle at some point in order for that promise to get resolved.

AngularJS Promise Callback Not Trigged in JasmineJS Test

Solution

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