Angularjs 我如何按照承诺和业力/角度模拟柴的延迟？

假装延迟承诺解决的示例测试：

describe('Example', function() {
  var $q;
  var $rootScope;
  var $scope;
  var $timeout;
  var fakePromise;

  beforeEach(inject(function (_$q_, _$rootScope_, _$timeout_) {
    $q = _$q_;
    $rootScope = _$rootScope_;
    $timeout = _$timeout_;
    $scope = $rootScope.$new();

    fakePromise = function (){
      return new Promise(function(resolve, reject){
        $timeout(function(){
          resolve('foo');
        }, 100);
      });
    };
  }));

  afterEach(function () {
    $scope.$apply();
  });

  it('should wait for promise to resolve and have a result', function(){
    return fakePromise().should.eventually.equal('foo'); //taken from chai-as-promised readme
  });

}))

自述文件说要做：

return doSomethingAsync().should.eventually.equal("foo");

我得到的错误是：

Chrome 49.0.2623 (Mac OS X 10.11.4) Example should wait for promise to resolve and have a result FAILED
  Error: timeout of 2000ms exceeded. Ensure the done() callback is being called in this test.

---

$timeout

服务已返回承诺。不需要制造

fakePromise = $timeout(function() {return "foo"}, 100);

---

在本例中，

fakePromise

被设置为一个在100毫秒后解析为“foo”的承诺。

这个怎么样？触发

done（）