MVC Unit Test with Mock

APIController.cs

public class HomeController : Controller
{
  public ActionResult Index()
  {
    return Json(true, JsonRequestBehavior.AllowGet);
  }
}

APITest.cs

[TestClass]
public class APITest
{
  private static string invalidSessionKey = "NotAValidKey";
  
  [TestMethod]
  public void AccessAPIWithValidSessionKey()
  {
      ApiHomeController c = new ApiHomeController();
      var mocks = new ContextMocks(c);
      var request = mocks.Request;
      var response = mocks.Response;

      request.SetupGet(x => x.Headers).Returns(
          new System.Net.WebHeaderCollection {
              {"SessionKey", invalidSessionKey}
          }
      );

      //System.Diagnostics.Debugger.Break();

      Assert.IsTrue(response.Object.StatusCode == 401);
  }
}

ContextMocks.cs

class ContextMocks
    {
        public Mock<HttpContextBase> HttpContext { get; set; }
        public Mock<HttpRequestBase> Request { get; set; }
        public Mock<HttpResponseBase> Response { get; set; }
        public RouteData RouteData { get; set; }

        public ContextMocks(Controller controller)
        {
            //define context objects
            HttpContext = new Mock<HttpContextBase>();
            Request = new Mock<HttpRequestBase>();
            Response = new Mock<HttpResponseBase>();

            HttpContext.Setup(x => x.Request).Returns(Request.Object);
            HttpContext.Setup(x => x.Response).Returns(Response.Object);
            //you would setup Response, Session, etc similarly with either mocks or fakes

            //apply context to controller
            RequestContext rc = new RequestContext(HttpContext.Object, new RouteData());
            controller.ControllerContext = new ControllerContext(rc, controller);
        }
    }