How to unit test ModelBind with Data Annotation validation ?

Question

I am working on asp.net mvc application using the mvc2 framework.

Here is the view.

<% using (Ajax.BeginForm("CreateMenuCategory",
           "Admin", 
           new AjaxOptions { UpdateTargetId = "tabs-MenuCategories", }))
       { %>
       <fieldset class="fields">
           <legend>
                Add Menu Categories
            </legend>
            <p>
                <label for="MenuCategoryName">MenuCategory Name:</label>
                <%= Html.TextBox("MenuCategoryName")%>
                <%= Html.ValidationMessage("MenuCategoryName")%>
            </p>
            <p>
                <label for="Description">Description</label>
                <%= Html.TextBox("Description")%>
                 <%= Html.ValidationMessage("Description")%>
            </p>               
            <p>
                <label for="Notes">Notes</label>
                <%= Html.TextBox("Notes")%>
            </p>        
             <p class="submit">
                    <input type="submit" value="Create" />
             </p>       
    </fieldset>
    <% } %>

Here is the Class I used for modelbinding

public class MenuCategoryBusinessObject
    {


        //private readonly IMenuRepository _repository;
        public int ID { get; set; }

        [Required]
        [StringLength(20)]
        public string MenuCategoryName { get; set; }

        [Required]
        [StringLength(20)]
        public string Description { get; set; }

        public string Notes { get; set; }

        public IEnumerable<MenuItemBusinessObject> MenuItems
        {
            get; set;
        }

    }

And here is my control

 [HttpPost]
    public ActionResult CreateMenuCategory([Bind(Exclude = "ID")]MenuCategoryBusinessObject  menuCategory)
    {

        if(ModelState.IsValid)
        {//if I am valid.
            _repository.CreateMenuCategory(menuCategory);
        }

        IndexMenuCategory model = new IndexMenuCategory
        {
            MenuCategories = _repository.GetMenuCategories(),
            SelectedMenuCategory = null

        };
        return PartialView("MenuCategories", model);
    }

When I do the model binding, the data annotation validation already knows the model is invalid and ModelState.IsValid is false.

However, when I do the unit test, if I feed my own MenuCategoryBusinessObject into the action method, it bypassed the modelbinding, and won't know the ModelState is invalid.

 [Fact]
    public void CreateNewMenuCategory()
    {
        // Setup
        DataStore dataStore = new DataStore();
        IMenuRepository menuRepository = new MenuRepository(dataStore);
        MenuCategoryBusinessObject menuCategoryBusinessObject =
            new MenuCategoryBusinessObject();
        AdminController adminControl = new AdminController(menuRepository);
        adminControl.SetFakeControllerContext();
        adminControl.Request.SetHttpMethodResult("POST");

        // Execute
        adminControl.CreateMenuCategory(menuCategoryBusinessObject);
    }

So, my questions is, how can effectively unit test in this situation?

Answer 1

In order to test if the model is correctly data annotated I would probably do something among the lines:

[TestMethod]
public void Description_Should_Be_Required()
{
    Expression<Func<MenuCategoryBusinessObject, object>> expression = 
        o => o.Description;
    var me = expression.Body as MemberExpression;
    var att = (RequiredAttribute[])me.Member
              .GetCustomAttributes(typeof(RequiredAttribute), false);
    att.Length.ShouldEqual(1);
}

The other thing you need to test is that you are effectively using the DataAnnotationsModelBinder instead of the default one:

ModelBinders.Binders.DefaultBinder = new DataAnnotationsModelBinder();

Answer 2

controllerInstance.ModelState.AddModelError("", "Dummy value.");

Adding a dummy value before the method is called will clear the IsValid flag. Then just call your action method to test this particular code path.