How do you Moq a .resx that lives in App_GlobalResource?

I'm writing unit tests for a controller in an MVC3 web project, but my tests throw exceptions when they try and access a resource like this:

return Index(Resources.Strings.MyStringResource);

The resource is a .resx file titled Strings.

I'm using the Moq libraries to achieve unit test for HttpContextBase functionality, so I was wondering how I would go about using the Moq libraries to access an App_GlobalResource.

Any help or pointers would be greatly appreciated!

You can't, at least not directly. The strongly-typed classes that are generated from resource (.resx) files expose static, not instance methods.

Because of this, they can't implement an interface method, nor are they virtual; Moq requires that at least one of these conditions are met in order to create a mock.

To get around this, you would create an abstraction, like anything else:

public interface IResources
{
    string MyStringResource { get; }
}

You'd pass (or inject) an implementation of this into your controller, and then pass that to your Index method. That implementation might look something like this:

public class ResourcesWrapper : IResources
{
    public string MyStringResource 
    { 
        get 
        { 
            return Resources.Strings.MyStringResource; 
        } 
    }
}

Then, when you're testing, you can use Moq to create a mock of the IResources interface, and pass that to your controller, like so:

// Create the mock.
var mock = new Mock<IResources>();

// Setup the property.
mock.SetupProperty(m => m.MyStringResource, "My Mocked Value");

// Pass the object somewhere for use.
Assert.AreEqual(mock.Object.MyStringResource, "My Mocked Value");