How to unit test a custom actionresult

Question

I'm trying to unit test a custom action result. I recently watched Jimmy Bogard's excellent MvcConf video ("put your controllers on a diet") http://www.viddler.com/explore/mvcconf/videos/1/ and have started to try and implement some custom action results. I've managed that without a problem, the ActionResult works fine at runtime but I'm having trouble trying to unit test them.

Unfortunately in the code download there are no unit tests for Jimmy's custom action methods... which make me wonder.

I realise that action methods just return instances of the ActionResult types and its the MVC framework that actually calls the ExecuteResult method, which of course is not available when running the unit test. So my unit test is now just creating an instance of my custom ActionResult and I then call ExecuteResult.

Unfortunatley in the ExecuteResult method of my custom ActionResult it is also calling the ExecuteResult method of a ViewResult that I passed it. At that point it blows up. How should I be mocking/stubbing these things to get my unit test working?

public class SendToAFriendActionResult : ActionResult
{

    public const string INVALID_CAPTCHA = "You don't appear to have filled out the two words from the security image correctly to prove you're a human. Please try again.";
    public const string INVALID_MODEL_STATE = "You don't appear to have filled out all the details correctly. Please try again.";
    public const string CONTACT_FAIL = "Unfortunately we experiend a problem sending the link. Please try again later.";
    public const string SEND_TO_A_FRIEND_FAIL_KEY = "ContactFail";

    private  RedirectResult _success;
    private  ViewResult _failure;
    private readonly SendToAFriendModel _model;
    private readonly bool _captchaValid;
    private readonly MessageBuilderServiceBase _mbs;

    public RedirectResult Success
    {
        get { return _success; }
        set { _success = value; }
    }

    public ViewResult Failure
    {
        get { return _failure; }
        set { _failure = value; }
    }

    public SendToAFriendActionResult(RedirectResult success, ViewResult failure, SendToAFriendModel model, bool captchaValid, MessageBuilderServiceBase mbs)
    {
        _success = success;
        _failure = failure;
        _model = model;
        _captchaValid = captchaValid;
        _mbs = mbs;
    }

    public override void ExecuteResult(ControllerContext context)
    {

        if (!_captchaValid)
        {
            Failure.TempData[SEND_TO_A_FRIEND_FAIL_KEY] = INVALID_CAPTCHA;

            // On reaching this point I receive the error
            // Object reference not set to an instance of an object
            // as the MVC framework calls FindView 
            Failure.ExecuteResult(context);
            return;
        }

        if (!context.Controller.ViewData.ModelState.IsValid)
        {
            Failure.TempData[SEND_TO_A_FRIEND_FAIL_KEY] = INVALID_MODEL_STATE;
            Failure.ExecuteResult(context);
            return;
        }

        _mbs.RecipientEmailAddress = _model.EmailRecipient;
        _mbs.SendersName = _model.SendersName;
        _mbs.Url = _model.URL;
        var result = _mbs.sendMessage();

        if (!result)
        {
            Failure.TempData[SEND_TO_A_FRIEND_FAIL_KEY] = CONTACT_FAIL;
            Failure.ExecuteResult(context);
            return;
        }

        Success.ExecuteResult(context);
    }
}

Here's the start of my unit test ...

        IMessageService _emailMessageSerivce;
        IGalleryRepository _repository;

        var stfModel = new SendToAFriendModel
        {
            SendersName = "Someone",
            URL = "http://someurl.com",
            EmailRecipient = "a-friend@somewherelse.com"
        };

        var failure = new ViewResult() {ViewName ="SendToFriend"};
        const bool captchaValid = false;
        var fakeControlllerContext = MockRepository.GenerateStub<ControllerContext>(null);

        var stf = new SendToAFriendActionResult(null, failure, stfModel, captchaValid, null);
        stf.ExecuteResult(fakeControlllerContext);

I've put comments in the SUT to show were the problem occurs.

I know I should be stubbing/mocking somehow but I just can't seem to resolve this.

Answer 1

From ASP.NET MVC 2 In Action (coauthored by Jimmy Bogard):

By taking that hard-to-test code out of an action and putting it into the Execute method of an action result, you ensure that the actions become significantly easier to unit-test. That’s because when you unit-test an action, you assert the type of action result that the action returns and the state of the action result. The Execute method of the action result isn’t executed as part of the unit test.

Unit tests are designed to isolate behavior and concerns. You're mixing concerns by calling ExecuteResult from within your custom Action. Instead, I would have the SendToAFriendActionResult return the actual ActionResult (Failure or Success):

public ActionResult GetAction(..)
{
   ActionResult result;
   //logic here to determine which ActionResult to return
   return result;
}

In your Controller:

  public ViewResult SendToAFriend()
    {
       return SendToAFriendActionResult(null, failure, stfModel, captchaValid, null)
            .GetAction();
    }

This method will allow the MVC framework to do its job and isolates those concerns outside your custom ActionResult. Your test should assert that the correct type of Action, failure or success, is returned based on the parameters you set going in.