UpdateModel, FormCollection and Unit Test

· March 29, 2009

ASP.NET MVC - Sprint Planner Helper   TDD

I ran into some problems with an Action Controller method that accepted a FormCollection. Inside the method, I use UpdateModel to get the values from the form into the model class.

Here is a skeleton implementation of the method:

UPDATED Some insightful comments by Steve made me do some changes to this code. I have now updated it. The tip had to do with if the ValueProvider should be set on the Controller in the test or in the actual Action method. I finally opted for the latter and changed it into this (significant code in bold).

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(FormCollection form)
{
    // Create ViewData
    ProductForm viewData = new ProductForm(new Product(), productOwnerRepository.Find().ToList());

    try
    {
        **UpdateModel(viewData, form.ToValueProvider());**

        // Get the product owner for the selected product-owner id
        viewData.Product.Owner = productOwnerRepository.GetById(viewData.SelectedOwnerID);

        // Add new product to the repository
        productRepository.Add(viewData.Product);
        productRepository.Save();

        // Go back to the list
        return RedirectToAction("Index");
    }
    catch
    {
        ModelState.AddRuleViolations(viewData.Product.GetRuleViolations());
        return View(viewData);
    }
}

This works great, but when I call this from my unit test, the values of my form (created in the unit test) are lost. I was very puzzled by this until I found this post in the ASP.NET MVC forum.

So what that means is that, in the unit test case, you need to set the ValueProvider for the controller you’re testing to the test form collection you’re sending to the method. Otherwise, the Action Controller method will check the Request property, which will be empty in the test case. Not obvious maybe, but understandable when you think about it.

UPDATED Just to be sure – note that the Action method is using an overloaded version of UpdateModel that makes sure that the sent-in form is used. I haven’t used the recommendation from the link above since I think it’s less readable/understandable. The main point is still valid though.

Here is a short sample that tests the action method above:

[TestMethod]
public void CreateControllerActionCanTakeAFormCollectionWithProductDataAndAddItToTheRepository()
{
    var numberOfProductsBefore = productRepository.Find().Count();
    var form = CreateProductTestFormCollection();
    
    var result = productController.Create(form);
    
    Assert.IsNotNull(result);
    Assert.IsInstanceOfType(result, typeof(RedirectToRouteResult));
    var redirectResult = (RedirectToRouteResult)result;
    Assert.AreEqual("Index", redirectResult.RouteValues["action"]);
    Assert.AreEqual(numberOfProductsBefore + 1, productRepository.Find().Count());
}

private static FormCollection CreateProductTestFormCollection()
{
    FormCollection form = new FormCollection();
    form.Add("Product.Name", TESTFORM_NAME);
    form.Add("Product.Description", TESTFORM_DESCRIPTION);
    form.Add("SelectedOwnerID", TestData.TEST_PRODUCTOWNER_ID2.ToString());

    return form;
}

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