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

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.

Answer 2

I've adjusted variable and injected dependency names on this to keep things clear as test writing continues. If done() is a function inside your (controller? directive? service/factory?) then it should be called when the test runs without trying to pass it in as a dependency. Ideally done() should be spied upon, but without knowing where it comes from it is impossible to show you how to set up the spy function.
The only other detail missing is that you have no expect() in this test suite. Without it I have no way to know what you are expecting to be asserted.
describe('PouchDB', function () {
var scope, db, q, rootScope;
beforeEach(
inject(
function(_$rootScope_, _$q_){
rootScope = _$rootScope_;
scope = rootScope.$new();
q = _$q_;
}
)
);
it("should run", function(){
//spy should be constructed here
function getPromise() {
var deferred = q.defer();
deferred.resolve(1);
return deferred.promise;
}
q.when(getPromise)
.then(function () {
done();
});
scope.$digest();
//assertion should be here
});
});