public async Task AddSubscription_ActivitiesEndPoint_WithoutSubscriberId()
        {
            Action <HttpRequestMessage> additionalChecks = message =>
            {
                Assert.AreEqual(0, message.Headers.Count());
            };

            FitbitClient fitbitClient = SetupFitbitClient("AddSubscriptionResponse.json", "https://api.fitbit.com/1/user/-/activities/apiSubscriptions/323-activities.json", HttpMethod.Post, additionalChecks);

            ApiSubscription response = await fitbitClient.AddSubscriptionAsync(APICollectionType.activities, "323");

            Assert.AreEqual("323", response.SubscriptionId);
        }
        public async Task AddSubscription_ActivitiesEndPoint_WithSubscriberId()
        {
            Action <HttpRequestMessage> additionalChecks = message =>
            {
                Assert.AreEqual(1, message.Headers.Count());
                Assert.IsTrue(message.Headers.Contains(Constants.Headers.XFitbitSubscriberId));

                IEnumerable <string> headerValues;
                Assert.IsTrue(message.Headers.TryGetValues(Constants.Headers.XFitbitSubscriberId, out headerValues));

                Assert.AreEqual(SubScriberId, headerValues.First());
            };

            FitbitClient fitbitClient = SetupFitbitClient("AddSubscriptionResponse.json", "https://api.fitbit.com/1/user/-/activities/apiSubscriptions/323-activities.json", HttpMethod.Post, additionalChecks);

            ApiSubscription response = await fitbitClient.AddSubscriptionAsync(APICollectionType.activities, "323", SubScriberId);

            Assert.AreEqual("323", response.SubscriptionId);
        }