Unit tests on MVC validation

Question

How can I test that my controller action is putting the correct errors in the ModelState when validating an entity, when I\'m using DataAnnotation validation in MVC 2 Previe

Answer 1

I'm using ModelBinders in my test cases to be able to update model.IsValid value.

var form = new FormCollection();
form.Add("Name", "0123456789012345678901234567890123456789");

var model = MvcModelBinder.BindModel(controller, form);

ViewResult result = (ViewResult)controller.Add(model);

With my MvcModelBinder.BindModel method as follows (basically the same code used internally in the MVC framework):

        public static TModel BindModel(Controller controller, IValueProvider valueProvider) where TModel : class
        {
            IModelBinder binder = ModelBinders.Binders.GetBinder(typeof(TModel));
            ModelBindingContext bindingContext = new ModelBindingContext()
            {
                FallbackToEmptyPrefix = true,
                ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, typeof(TModel)),
                ModelName = "NotUsedButNotNull",
                ModelState = controller.ModelState,
                PropertyFilter = (name => { return true; }),
                ValueProvider = valueProvider
            };

            return (TModel)binder.BindModel(controller.ControllerContext, bindingContext);
        }