public async Task Users_AfterRefresh_IsPopulated()
        {
            // Arrange
            var dataService = new FakeDataService();
            var viewModel   = new UserViewModel(dataService);

            // Act
            await viewModel.RefreshUsers();

            // Assert
            Assert.IsNotNull(viewModel.Users);
            Assert.AreEqual(2, viewModel.Users.Count());
        }
        public async Task Users_AfterClear_IsEmpty()
        {
            // Arrange
            var dataService = new FakeDataService();
            var viewModel   = new UserViewModel(dataService);
            await viewModel.RefreshUsers();

            Assert.AreEqual(2, viewModel.Users.Count());

            // Act
            viewModel.ClearUsers();

            // Assert
            Assert.IsNotNull(viewModel.Users);
            Assert.AreEqual(0, viewModel.Users.Count());
        }