Rhino mock of inherited class

Question

Im trying to mock System.Web.Mvc.ModelStateDictionary which does not have virtual methods. So I've tried to make a sub class in this way:

public abstract class ModelStateDictionaryMock : ModelStateDictionary
{
    public new abstract int Count { get; }

    public new abstract bool IsReadOnly { get; }

    public new abstract bool IsValid { get; }

    public new abstract ICollection<string> Keys { get; }

    public new abstract ICollection<ModelState> Values { get; }

    public new abstract ModelState this[string key] { get; set; }

    public new abstract void Add(KeyValuePair<string, ModelState> item);

    public new abstract void Add(string key, ModelState value);

    public new abstract void AddModelError(string key, Exception exception);

    public new abstract void AddModelError(string key, string errorMessage);

    public new abstract void Clear();

    public new abstract bool Contains(KeyValuePair<string, ModelState> item);

    public new abstract bool ContainsKey(string key);

    public new abstract void CopyTo(KeyValuePair<string, ModelState>[] array, int arrayIndex);

    public new abstract IEnumerator<KeyValuePair<string, ModelState>> GetEnumerator();

    public new abstract bool IsValidField(string key);

    public new abstract void Merge(ModelStateDictionary dictionary);

    public new abstract bool Remove(KeyValuePair<string, ModelState> item);

    public new abstract bool Remove(string key);

    public new abstract void SetModelValue(string key, ValueProviderResult value);

    public new abstract bool TryGetValue(string key, out ModelState value);
}

However when I generate a mock using var modelStateDictionary = MockRepository.GenerateMock<ModelStateDictionaryMock>(); I get an object which has a double set of properties, like this:

Doing modelStateDictionary.Count accesses the base property, so my mock does not work. Does anyone know how to get around this problem?

Because the properties are not overridden. You've just shadowed them using `new` keyword. — Sriram Sakthivel, Feb 24 '16 at 07:49
When you have the opportunity, you can consider using Microsoft Fakes (if you have the correct Visual Studio version). — Complexity, Feb 24 '16 at 07:50
@Complexity thanks. It works using MS Fakes. I'm doing `System.Web.Mvc.Fakes.ShimModelStateDictionary.AllInstances.AddModelErrorStringString = (dictionary, key, errorMessage) => { Assert.Fail(errorMessage); };` — magnusarinell, Feb 24 '16 at 09:01
Arrgh, all this mess because MS didnt do virtual or interface. — magnusarinell, Feb 24 '16 at 09:02
you don't need to mock this class at all... just create a new instance of `ModelStateDictionary` and then use it in your UT... — Old Fox, Feb 25 '16 at 16:17
@OldFox how can I then react to writes to that ModelStateDictionary? — magnusarinell, Feb 25 '16 at 17:26
@Drutten I don't understand your question.... you can use any method `ModelStateDictionary` has... — Old Fox, Feb 25 '16 at 18:12

score 0 · Accepted Answer · edited May 23 '17 at 12:13

You get double set of properties because you are defining the methods in your mock class as using the "new" keyword. This treats the method as a new method, and has nothing to do with the base method.

Also, because the base class method is not abstract or virtual, you really can't override it.

As for solving your mocking problem, normally there is no need to mock the ModelState dictionary.. once you have the controller reference, you get access to its ModelState, where you can setup the model errors etc. using the real object, and not mocking it.

Look at this post for details on how to setup errors on the Model State: How to mock ModelState.IsValid using the Moq framework?

I want to mock `ModelState` for two reasons: 1. To make sure that any errors added are actually failing the test. Otherwise I need to check `ModelState` after the test and that may be missed out. 2. To get the failing line in the controller. — magnusarinell, Feb 24 '16 at 08:02

score 0 · Answer 2 · answered Feb 24 '16 at 07:53

0

You should setup your mock in order to have it return a value.

modelStateDictionary.Stub(x => x.Count).Return(10);

Now if you ask modelStateDictionary.Count it will return 10 instead of using the base implementation.

answered Feb 24 '16 at 07:53

GuyVdN

690
4
14

I'm afraid it won't. – magnusarinell Feb 24 '16 at 08:04
Can you show some more code then. Copied your class and wrote this little test that seems to work. `var modelStateDictionary = MockRepository.GenerateMock(); modelStateDictionary.Stub(x => x.Count).Return(10); Assert.That(modelStateDictionary.Count, Is.EqualTo(10));` – GuyVdN Feb 24 '16 at 08:10
Try `(modelStateDictionary as ModelStateDictionary).Count`. It returns 0. – magnusarinell Feb 24 '16 at 08:17
Why do you need to perform a cast? – GuyVdN Feb 24 '16 at 08:26
It is implicitly casted since the type of `ModelState` is `ModelStateDictionary` – magnusarinell Feb 24 '16 at 08:36

Rhino mock of inherited class

2 Answers2