I'm trying to start using Unit Testing and I want to test the following Controller:

public class AjaxController : Controller {

...

    public JsonResult RateVideo( int userRating, long videoId )
    {

        string userName = User.Identity.Name;

... }

}

I have a created a TestClass with the following method:

[ TestMethod public void TestRateVideo()

    {            

        //Arrange
        AjaxController c = new AjaxController();

        //Act
        JsonResult jr = c.RateVideo(1, 1);



        //Assert
        //Not implemented yet

    }

I select debug and run the test. When the code reaches the 1st statement:

string username = User.Identity.Name;

Debugging stops and I am presented with a message that says that the test failed.

Any guidance you can offer would be appreciated.