c# - NullReferenceException thrown when testing custom AuthorizationAttribute

I have taken a look at:

I am trying to test a custom AuthorizeAttribute that I wrote.

I have tried many different things to get it to work. This is my current attempt.

[AttributeUsage(AttributeTargets.All, AllowMultiple = false, Inherited = true)]
public class ConfigurableAuthorizeAttribute : AuthorizeAttribute
{
    private Logger log = new Logger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
    private IRoleHelper roleHelper;
    public ConfigurableAuthorizeAttribute()
    {
        roleHelper = new ADRoleHelper();
    }
    public ConfigurableAuthorizeAttribute(IRoleHelper roleHelper)
    {
        this.roleHelper = roleHelper;
    }
    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        if (!httpContext.User.Identity.IsAuthenticated)
        {
            return false;
        }
        if (this.roleHelper.IsUserInRole(this.Roles, HttpContext.Current.User.Identity.Name))
        {
            return true;
        }
        return false;
    }
    protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
    {
        base.HandleUnauthorizedRequest(filterContext);
        filterContext.Result = new RedirectResult("~/home/Unauthorized");
    }
}

[Test]
public void unauthenticated_user_not_allowed_to_access_resource()
{
    var user = new Mock();
    user.Setup(u => u.Identity.IsAuthenticated).Returns(false);
    var authContext = new Mock();
    authContext.Setup(ac => ac.HttpContext.User).Returns(user.Object);
    var configAtt = new ConfigurableAuthorizeAttribute();
    configAtt.OnAuthorization(authContext.Object);
    authContext.Verify(ac => ac.Result == It.Is(r => r.Url == ""));
}

No matter what I do I always get a System.NullReferenceException when I run the test. It never seems to get past the OnAuthorization call. The stack trace is as follows:

Result Message: System.NullReferenceException : Object reference not
set to an instance of an object. Result StackTrace: at
System.Web.Mvc.OutputCacheAttribute.GetChildActionFilterFinishCallback(ControllerContext
controllerContext) at
System.Web.Mvc.AuthorizeAttribute.OnAuthorization(AuthorizationContext
filterContext) at
...ConfigurableAuthorizeAttributeTests.unauthenticated_user_not_allowed_to_access_resource()
in ...ConfigurableAuthorizeAttributeTests.cs:line
29

Does anybody have any ideas on how to solve this problem?

Edit

I found the solution. I also needed to mock ControllerDescriptor and make sure that HttpContextBase.Items returned a new Dictionary.

Working code:

var context = new Mock();
context.Setup(c => c.Items).Returns(new Dictionary());
context.Setup(c => c.User.Identity.IsAuthenticated).Returns(false);
var controller = new Mock();
var actionDescriptor = new Mock();
actionDescriptor.Setup(a => a.ActionName).Returns("Index");
var controllerDescriptor = new Mock();
actionDescriptor.Setup(a => a.ControllerDescriptor).Returns(controllerDescriptor.Object);
var controllerContext = new ControllerContext(context.Object, new RouteData(), controller.Object);
var filterContext = new AuthorizationContext(controllerContext, actionDescriptor.Object);
var att = new ConfigurableAuthorizeAttribute();
att.OnAuthorization(filterContext);
Assert.That(filterContext.Result, Is.InstanceOf());
Assert.That(((RedirectResult)filterContext.Result).Url, Is.EqualTo("~/home/Unauthorized"));