Angular $q.when is not resolved in Karma unit test

Question

I use $q.when to wrap around other lib promises. It works like a charm but when i try to run it inside Karma the promise failes to resolve (done() is never executed) even if I ran $digest and even after timeout. Here is sample code:

describe('PouchDB', function () {
var $q, $rootScope;

beforeEach(inject(function (_$rootScope_, _$q_) {
    $rootScope = _$rootScope_;
    $q = _$q_;
}));

it("should run", function (done) {

    function getPromise() {
        var deferred = Q.defer();

        deferred.resolve(1);

        return deferred.promise;
    }

    $q.when(getPromise())
        .then(function () {
            done();   // this never runs
        });

    $rootScope.$digest();
});

Why? What is the cause of this? I really cannot get it.

Update (workaround)

I do not understand why $q.when is not resolved in Karma - it has something with nextTick function but I cannot debug the problem. Instead I ditched $q.when and wrote simple function that converts PouchDB (or any other like Q) to $q:

.factory('$utils', function ($q, $rootScope) {
  return {
    to$q: function (promise) {
      var deferred = $q.defer();

      promise.then(function (result) {
        deferred.resolve(result);
        $rootScope.$digest();
      });

      promise.catch(function (error) {
        deferred.reject(error);
        $rootScope.$digest();
      });

      return deferred.promise;
    }
  }
})

Answer 1

From How to resolve $q.all promises in Jasmine unit tests? it seems the trick is:

$rootScope.$apply();

I just had the same problem and this works for me; the promises are resolved on making this call.