public void EnableClientValidation() {
// Arrange
var mockViewContext = new Mock<ViewContext>();
var viewDataContainer = new Mock<IViewDataContainer>().Object;
var htmlHelper = new HtmlHelper(mockViewContext.Object, viewDataContainer);
// Act
htmlHelper.EnableClientValidation();
// Act & assert
mockViewContext.VerifySet(vc => vc.ClientValidationEnabled = true);
}