Unit-test promise-based code in Angularjs

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You will still need to mock the services and return a promise, but you should use real promises instead, so you don’t need to implement its functionality. Use beforeEach to create the already fulfilled promise and mock the service if you need it to ALWAYS be resolved.

var $rootScope;

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

  var deferred = $q.defer();
  deferred.resolve('somevalue'); //  always resolved, you can do it from your spec

  // jasmine 2.0
  spyOn(tasksService, 'removeAndGetNext').and.returnValue(deferred.promise); 

  // jasmine 1.3
  //spyOn(tasksService, 'removeAndGetNext').andReturn(deferred.promise); 

}));

If you’d rather prefer to resolve it in each it block with a different value, then you just expose the deferred to a local variable and resolve it in the spec.

Of course, you would keep your tests as they are, but here is some really simple spec to show you how it would work.

it ('should test receive the fulfilled promise', function() {
  var result;

  tasksService.removeAndGetNext().then(function(returnFromPromise) {
    result = returnFromPromise;
  });

  $rootScope.$apply(); // promises are resolved/dispatched only on next $digest cycle
  expect(result).toBe('somevalue');
});

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