ASP.NET MVC unit test controller with HttpContext

Question

I am trying to write a unit test for my one controller to verify if a view was returned properly, but this controller has a basecontroller that accesses the HttpContext.Current.Session. Everytime I create a new instance of my controller is calls the basecontroller constructor and the test fails with a null pointer exception on the HttpContext.Current.Session. Here is the code:

public class BaseController : Controller {            protected BaseController()     {        ViewData["UserID"] = HttpContext.Current.Session["UserID"];        } }  public class IndexController : BaseController {     public ActionResult Index()     {         return View("Index.aspx");     } }      [TestMethod]     public void Retrieve_IndexTest()     {         // Arrange         const string expectedViewName = "Index";          IndexController controller = new IndexController();          // Act         var result = controller.Index() as ViewResult;          // Assert         Assert.IsNotNull(result, "Should have returned a ViewResult");         Assert.AreEqual(expectedViewName, result.ViewName, "View name should have been {0}", expectedViewName);     } 

Any ideas on how to mock (using Moq) the Session that is accessed in the base controller so the test in the descendant controller will run?

Answer 1

Unless you use Typemock or Moles, you can't.

In ASP.NET MVC you are not supposed to be using HttpContext.Current. Change your base class to use ControllerBase.ControllerContext - it has a HttpContext property that exposes the testable HttpContextBase class.

Here's an example of how you can use Moq to set up a Mock HttpContextBase:

var httpCtxStub = new Mock<HttpContextBase>();  var controllerCtx = new ControllerContext(); controllerCtx.HttpContext = httpCtxStub.Object;  sut.ControllerContext = controllerCtx;  // Exercise and verify the sut 

where sut represents the System Under Test (SUT), i.e. the Controller you wish to test.

Answer 2

If you are using Typemock, you can do this:

Isolate.WhenCalled(()=>controller.HttpContext.Current.Session["UserID"]) .WillReturn("your id"); 

The test code will look like:

[TestMethod] public void Retrieve_IndexTest() {     // Arrange     const string expectedViewName = "Index";      IndexController controller = new IndexController();     Isolate.WhenCalled(()=>controller.HttpContext.Current.Session["UserID"])     .WillReturn("your id");     // Act     var result = controller.Index() as ViewResult;      // Assert     Assert.IsNotNull(result, "Should have returned a ViewResult");     Assert.AreEqual(expectedViewName, result.ViewName, "View name should have been {0}", expectedViewName); }