c# - ASP.NET MVC Controller post method unit test: ModelState.IsValid always true

Question

I have written my first unit tests for an ASP.NET MVC web application. All works fine and it is giving me valuable information, but I can't test errors in the view model. The ModelState.IsValid is always true, even when some values are not filled in (empty string or null).

I have read already that the model validation happens when the posted data is mapped to the model and you need to write some code to do the model verification yourself:

• Geek With Blogs
• How can I test ModelState?

I have tried the three examples provided in the linked webpages, but it seems not to work for me.

Some code:

My viewmodel

...
[Required(ErrorMessageResourceName = "ErrorFirstName", ErrorMessageResourceType = typeof(Mui))]
[MaxLength(50)]
[Display(Name = "Firstname", ResourceType = typeof(Mui))]
public string FirstName { get; set; }
...

The controller

...
 [HttpPost]
    public ActionResult Index(POSViewModel model)
    {
        Contract contract = contractService.GetContract(model.ContractGuid.Value);

        if (!contract.IsDirectDebit.ToSafe())
        {
            ModelState.Remove("BankName");
            ModelState.Remove("BankAddress");
            ModelState.Remove("BankZip");
            ModelState.Remove("BankCity");
            ModelState.Remove("AccountNr");
        }

        if (ModelState.IsValid)
        {
            ...

            contractValidationService.Create(contractValidation);
            unitOfWork.SaveChanges();

            return RedirectToAction("index","thanks");
        }
        else
        {
            return Index(model.ContractGuid.ToString());
        }
    }

My unit test

  posViewModel.FirstName = null;
  posViewModel.LastName = "";
 ...
 var modelBinder = new ModelBindingContext()
        {
            ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => posViewModel, posViewModel.GetType()),
            ValueProvider = new NameValueCollectionValueProvider(new System.Collections.Specialized.NameValueCollection(), CultureInfo.InvariantCulture)
        };
        var binder = new DefaultModelBinder().BindModel(new ControllerContext(), modelBinder);
        posController.ModelState.Clear();
        posController.ModelState.Merge(modelBinder.ModelState);

        ActionResult result = posController.Index(posViewModel);

        //Assert
        mockContractValidationService.Verify(m => m.Create(It.IsAny<ContractValidation>()), Times.Never);
        Assert.IsInstanceOfType(result, typeof(ViewResult));

On the view, I'm using unobtrusive JavaScript validation, and it works.

Answer 1

You're trying to test two different things at the same time. The controller is not reponsible for validating the model state, only for behaving differently based on the result of that validation. So your unit tests for the controller shouldn't try to test the validation, that should be done in a different test. In my opinion you should have three unit tests:

1. One that verifies whether model validation correctly
2. One that validates whether the controller behaves correctly when modelstate is valid
3. One that validates whether the controller behaves correctly when modelstate is invalid

Here's how you can do that:

1.Model validation

[Test]
public void test_validation()
{
    var sut = new POSViewModel();
    // Set some properties here
    var context = new ValidationContext(sut, null, null);
    var results = new List<ValidationResult>();
    var isModelStateValid =Validator.TryValidateObject(sut, context, results, true);

    // Assert here
}

2.Controller with invalid modelstate

[Test]
public void test_controller_with_model_error()
{
    var controller = new PosController();
    controller.ModelState.AddModelError("test", "test");

    ActionResult result = posController.Index(new PosViewModel());

    // Assert that the controller executed the right actions when the model is invalid
}

3.Controller with valid modelstate

[Test]
public void test_controller_with_valid_model()
{
    var controller = new PosController();
    controller.ModelState.Clear();

    ActionResult result = posController.Index(new PosViewModel());

    // Assert that the controller executed the right actions when the model is valid
}