public Task TestExistsAsync()
        {
            var storageController = new Mock<IStorageController>();
              var mockedStorage = new Mock<IStorageDictionary<string, object>>();
              var controller = new AVCurrentUserController(storageController.Object);
              var user = new AVUser();

              storageController.Setup(c => c.LoadAsync()).Returns(Task.FromResult(mockedStorage.Object));

              bool contains = false;
              mockedStorage.Setup(s => s.AddAsync("CurrentUser", It.IsAny<object>())).Callback(() => {
            contains = true;
              }).Returns(Task.FromResult<object>(null)).Verifiable();

              mockedStorage.Setup(s => s.RemoveAsync("CurrentUser")).Callback(() => {
            contains = false;
              }).Returns(Task.FromResult<object>(null)).Verifiable();

              mockedStorage.Setup(s => s.ContainsKey("CurrentUser")).Returns(() => contains);

              return controller.SetAsync(user, CancellationToken.None).OnSuccess(_ => {
            Assert.AreEqual(user, controller.CurrentUser);

            return controller.ExistsAsync(CancellationToken.None);
              }).Unwrap()
              .OnSuccess(t => {
            Assert.IsTrue(t.Result);

            controller.ClearFromMemory();
            return controller.ExistsAsync(CancellationToken.None);
              }).Unwrap()
              .OnSuccess(t => {
            Assert.IsTrue(t.Result);

            controller.ClearFromDisk();
            return controller.ExistsAsync(CancellationToken.None);
              }).Unwrap()
              .OnSuccess(t => {
            Assert.IsFalse(t.Result);
            mockedStorage.Verify();
              });
        }
        public Task TestLogOut()
        {
            var storageController = new Mock<IStorageController>(MockBehavior.Strict);
              var controller = new AVCurrentUserController(storageController.Object);
              var user = new AVUser();

              return controller.SetAsync(user, CancellationToken.None).OnSuccess(_ => {
            Assert.AreEqual(user, controller.CurrentUser);
            return controller.ExistsAsync(CancellationToken.None);
              }).Unwrap()
              .OnSuccess(t => {
            Assert.IsTrue(t.Result);

            return controller.LogOutAsync(CancellationToken.None);
              }).Unwrap().OnSuccess(_ => controller.GetAsync(CancellationToken.None)).Unwrap()
              .OnSuccess(t => {
            Assert.IsNull(t.Result);

            return controller.ExistsAsync(CancellationToken.None);
              }).Unwrap()
              .OnSuccess(t => {
            Assert.IsFalse(t.Result);
              });
        }