public async Task GatewayAccountReader_MessageHandler()
        {
            HttpMessageHandler messageHandler   = new CustomMessageHandler();
            HttpClient         staticHttpClient = new HttpClient(messageHandler);

            GatewayAccountReader accountReader = new GatewayAccountReader(
                serviceEndpoint: new Uri("https://localhost"),
                cosmosAuthorization: Mock.Of <AuthorizationTokenProvider>(),
                connectionPolicy: new ConnectionPolicy(),
                httpClient: MockCosmosUtil.CreateCosmosHttpClient(() => staticHttpClient));

            DocumentClientException exception = await Assert.ThrowsExceptionAsync <DocumentClientException>(() => accountReader.InitializeReaderAsync());

            Assert.AreEqual(HttpStatusCode.Conflict, exception.StatusCode);
        }
        public async Task GatewayAccountReader_MessageHandler()
        {
            HttpMessageHandler messageHandler   = new CustomMessageHandler();
            HttpClient         staticHttpClient = new HttpClient(messageHandler);

            GatewayAccountReader accountReader = new GatewayAccountReader(
                new Uri("https://localhost"),
                Mock.Of <IComputeHash>(),
                false,
                null,
                new ConnectionPolicy(),
                MockCosmosUtil.CreateCosmosHttpClient(() => staticHttpClient));

            DocumentClientException exception = await Assert.ThrowsExceptionAsync <DocumentClientException>(() => accountReader.InitializeReaderAsync());

            Assert.AreEqual(HttpStatusCode.Conflict, exception.StatusCode);
        }