Unit tests on MVC validation

Solution 1:

Hate to necro a old post, but I thought I'd add my own thoughts (since I just had this problem and ran across this post while seeking the answer).

1. Don't test validation in your controller tests. Either you trust MVC's validation or write your own (i.e. don't test other's code, test your code)
2. If you do want to test validation is doing what you expect, test it in your model tests (I do this for a couple of my more complex regex validations).

What you really want to test here is that your controller does what you expect it to do when validation fails. That's your code, and your expectations. Testing it is easy once you realize that's all you want to test:

[test]
public void TestInvalidPostBehavior()
{
    // arrange
    var mockRepository = new Mock<IBlogPostSVC>();
    var homeController = new HomeController(mockRepository.Object);
    var p = new BlogPost();

    homeController.ViewData.ModelState.AddModelError("Key", "ErrorMessage"); // Values of these two strings don't matter.  
    // What I'm doing is setting up the situation: my controller is receiving an invalid model.

    // act
    var result = (ViewResult) homeController.Index(p);

    // assert
    result.ForView("Index")
    Assert.That(result.ViewData.Model, Is.EqualTo(p));
}

Solution 2:

I had been having the same problem, and after reading Pauls answer and comment, I looked for a way of manually validating the view model.

I found this tutorial which explains how to manually validate a ViewModel that uses DataAnnotations. They Key code snippet is towards the end of the post.

I amended the code slightly - in the tutorial the 4th parameter of the TryValidateObject is omitted (validateAllProperties). In order to get all the annotations to Validate, this should be set to true.

Additionaly I refactored the code into a generic method, to make testing of ViewModel validation simple:

    public static void ValidateViewModel<TViewModel, TController>(this TController controller, TViewModel viewModelToValidate) 
        where TController : ApiController
    {
        var validationContext = new ValidationContext(viewModelToValidate, null, null);
        var validationResults = new List<ValidationResult>();
        Validator.TryValidateObject(viewModelToValidate, validationContext, validationResults, true);
        foreach (var validationResult in validationResults)
        {
            controller.ModelState.AddModelError(validationResult.MemberNames.FirstOrDefault() ?? string.Empty, validationResult.ErrorMessage);
        }
    }

So far this has worked really well for us.

Solution 3:

When you call the homeController.Index method in your test, you aren't using any of the MVC framework that fires off the validation so ModelState.IsValid will always be true. In our code we call a helper Validate method directly in the controller rather than using ambient validation. I haven't had much experience with the DataAnnotations (We use NHibernate.Validators) maybe someone else can offer guidance how to call Validate from within your controller.