unit testing - How to mock the Request on Controller in ASP.Net MVC?

Question

I have a controller in C# using the ASP.Net MVC framework

public class HomeController:Controller{
  public ActionResult Index()
    {
      if (Request.IsAjaxRequest())
        { 
          //do some ajaxy stuff
        }
      return View("Index");
    }
}

I got some tips on mocking and was hoping to test the code with the following and RhinoMocks

var mocks = new MockRepository();
var mockedhttpContext = mocks.DynamicMock<HttpContextBase>();
var mockedHttpRequest = mocks.DynamicMock<HttpRequestBase>();
SetupResult.For(mockedhttpContext.Request).Return(mockedHttpRequest);

var controller = new HomeController();
controller.ControllerContext = new ControllerContext(mockedhttpContext, new RouteData(), controller);
var result = controller.Index() as ViewResult;
Assert.AreEqual("About", result.ViewName);

However I keep getting this error:

Exception System.ArgumentNullException: System.ArgumentNullException : Value cannot be null. Parameter name: request at System.Web.Mvc.AjaxRequestExtensions.IsAjaxRequest(HttpRequestBase request)

Since the Request object on the controller has no setter. I tried to get this test working properly by using recommended code from an answer below.

This used Moq instead of RhinoMocks, and in using Moq I use the following for the same test:

var request = new Mock<HttpRequestBase>();
// Not working - IsAjaxRequest() is static extension method and cannot be mocked
// request.Setup(x => x.IsAjaxRequest()).Returns(true /* or false */);
// use this
request.SetupGet(x => x.Headers["X-Requested-With"]).Returns("XMLHttpRequest");

var context = new Mock<HttpContextBase>();
context.SetupGet(x => x.Request).Returns(request.Object);
var controller = new HomeController(Repository, LoginInfoProvider);
controller.ControllerContext = new ControllerContext(context.Object, new RouteData(), controller);
var result = controller.Index() as ViewResult;
Assert.AreEqual("About", result.ViewName);

but get the following error:

Exception System.ArgumentException: System.ArgumentException : Invalid setup on a non-overridable member: x => x.Headers["X-Requested-With"] at Moq.Mock.ThrowIfCantOverride(Expression setup, MethodInfo methodInfo)

Again, it seems like I cannot set the request header. How do I set this value, in RhinoMocks or Moq?

Answer 1

Using Moq:

var request = new Mock<HttpRequestBase>();
// Not working - IsAjaxRequest() is static extension method and cannot be mocked
// request.Setup(x => x.IsAjaxRequest()).Returns(true /* or false */);
// use this
request.SetupGet(x => x.Headers).Returns(
    new System.Net.WebHeaderCollection {
        {"X-Requested-With", "XMLHttpRequest"}
    });

var context = new Mock<HttpContextBase>();
context.SetupGet(x => x.Request).Returns(request.Object);

var controller = new YourController();
controller.ControllerContext = new ControllerContext(context.Object, new RouteData(), controller);

UPDATED:

Mock Request.Headers["X-Requested-With"] or Request["X-Requested-With"] instead of Request.IsAjaxRequest().