public async void GetSpeakerSessionCollection_OkResult() {
            var sessionObject = new RootObject()
            {
                Collection = new Collection()
                {
                    Items = new List<ResponseItem>()
                    {
                        new ResponseItem()
                        {
                            Id = 1
                        },
                        new ResponseItem()
                        {
                            Id = 2
                        },
                        new ResponseItem()
                        {
                            Id = 3
                        }
                    }
                }
            };
            var speakerObject = new RootObject()
            {
                Collection = new Collection()
                {
                    Items = new List<ResponseItem>()
                    {
                        new ResponseItem()
                        {
                            Id = 1
                        },
                        new ResponseItem()
                        {
                            Id = 2
                        }
                    }
                }
            };

            httpClientService.GetAsync<RootObject>("sessions").Returns<RootObject>(sessionObject);
            httpClientService.GetAsync<RootObject>("speakers").Returns<RootObject>(speakerObject);

            
            var result = await conferenceService.GetCollectionAsync();
            var model = Assert.IsAssignableFrom<SpeakerSessionCollection>(
                result);
            Assert.Equal(3, model.SessionsList.Count);
            Assert.Equal(2, model.SpeakersList.Count);
        }