Mocked method returns null

I have a simple test method in my Silverlight project:

[TestMethod]
[Tag("User")]
public void ViewModel_NewUserAdded_DefaultCulturesLoaded()
{
    //setup
    Mock<INameService> mockNameService = new Mock<INameService>();
    MainViewModel viewModel = new MainViewModel();
    mockNameService
        .Setup(m => m.DefaultCultures(It.IsAny<Action<LoadOperation<kk_mp_name>>>()))
        .Returns(new Mock<OperationBase>(null).Object);
    viewModel.ContextName = mockNameService.Object;

    //action
    Messenger.Default.Send(-1, "New User Added");

    //verify
    mockNameService.Verify(
        (mo) => mo.DefaultCultures(It.IsAny<Action<LoadOperation<kk_mp_name>>>()),
        Times.Exactly(1));
}

There DefaultCultures method always returns null instea开发者_JAVA百科d of new mock-object. What I doing wrong?

From your comments, it looks like

var mockNameService = new Mock<INameService>(MockBehavior.Strict);

didn't help much.

So my next point of query would be to ask why you're passing in Null here.

new Mock<OperationBase>(null).Object

Can you post the code for OperationBase ?

Is Messenger.Default.Send using the mock object you set on viewModel.ContextName? If you step into the code to the point where you expect the DefaultCultures to be invoked, you can check the concrete type of ContextName to ensure it is the mock instance.

I also find it helpful to add a .Callback on the mock set up, on which to set a breakpoint and ensure that the method is being invoked:

MainViewModel viewModel = new MainViewModel();
mockNameService
    .Setup(m => m.DefaultCultures(It.IsAny<Action<LoadOperation<kk_mp_name>>>()))
    .Callback((Action<LoadOperation<kk_mp_name>> a) =>
     {
         ; // Set breakpoint here
     })
    .Returns(new Mock<OperationBase>(null).Object);