ASP.NET MVC 3 beta: TryUpdateModel throws NullreferenceException in unit test

Question

Hi,

Since I updated to ASP.NET MVC 3 Beta 1, I get a NullReferenceException whenever I call TryUpdateModel() during a unit test session.

The stack trace looks like this:

Execute System.NullReferenceException: Object reference not set to an instance of an object. at System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext controllerContext) at System.Web.Mvc.ValueProviderFactoryCollection.<>c_DisplayClassc.b_7(ValueProviderFactory factory) at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() at System.Collections.Generic.List1..ctor(IEnumerable1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at System.Web.Mvc.ValueProviderFactoryCollection.GetValueProvider(ControllerContext controllerContext) at System.Web.Mvc.ControllerBase.get_ValueProvider() at Zeiterfassung.Controllers.ControllerBase1.TryUpdateModelAndTrackChanges[TModel](TModel model, String prefix) in C:\Users\Adrian\Documents\Sites\Zeiterfassung\Zeiterfassung\Controllers\ControllerBase.cs:line 164 ... My own code from here on...

The same action method works fine when running on the web server, so my guess is that it is a problem with Dependency Injection in unit testing.

Is there something I need to setup for this to work? I'd rather not revert to the previous ASP.NET MVC version if possible.

Answer 1

You need to mock the ControllerContext. Personally I use MvcContrib.TestHelper which is based on Rhino Mocks to achieve this:

// arrange
var controller = new HomeController();
new TestControllerBuilder().InitializeController(controller);

// act
var actual = controller.Index();

but any mocking framework could do the job. You just need to make sure that in your unit test controller.ControllerContext is not null.