Angular单元测试：测试简单的基于promise的功能

Question

I have a very simple mock service that I have created in my unit test for injecting into another object that I am testing.

beforeEach(inject(function($q, $timeout) {
  ItemService = {
    one: function(id) {
      var deferred = $q.defer();
      $timeout(function() {
        deferred.resolve({
          id: id
        });
      }, 0);
      return deferred.promise;
    }
  };
}));

Now I'd like to write a simple unit test that makes sure that this service returns the correct promise.

describe('mock service', function() {
  it('should return a promise', function() {
    // test comes here
    ItemService.one('123').then(function(item) {
      // ... but doesn't make it here
      expect(item.id).toEqual('123');
    });
  });  
});

However, the code inside then() never gets executed.

Answer 1

The $timeout service used in unit tests is a mocked $timeout service , that needs to be flushed (just like $httpBackend). This allows testing code that waits for 10 minutes without actually waiting for 10 minutes in the test:

ItemService.one('123').then(function(item) {
  // ... but doesn't make it here
  expect(item.id).toEqual('123');
});
$timeout.flush(1);

I'm not sure that this automatically resolves the promise though, because promises are resolved the the scope is $applied. So you might additionally need

$rootScope.$apply();

Of course, $timeout and $rootScope need to be injected in the test.