public void Error_WhenValid_ReturnsEmptyString()
        {
            // arrange
            var vm = new FakeScreenViewModel();
            vm.Validator = new ValidWhenPropertyOneIsGreaterThan100Validator();
            vm.PropertyOne = 101;

            // action
            vm.Validate();

            // assert
            Assert.IsTrue(string.IsNullOrWhiteSpace(vm.Error));
        }
        public void Indexer_WhenNotValid_ReturnsPropertyErrorMessage()
        {
            // arrange
            var vm = new FakeScreenViewModel();
            vm.Validator = new ValidWhenPropertyOneIsGreaterThan100Validator();
            vm.PropertyOne = 99;

            // action
            vm.Validate();

            // assert
            Assert.IsFalse(string.IsNullOrWhiteSpace(vm["PropertyOne"]));
        }
        public void Validate_WhenValid_ReturnsTrue()
        {
            // arrange
            var vm = new FakeScreenViewModel();
            vm.Validator = new ValidWhenPropertyOneIsGreaterThan100Validator();
            vm.PropertyOne = 101;

            // action
            var result = vm.Validate();

            // assert
            Assert.IsTrue(result);
        }