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

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().

For anyone using NSubstitute I was able to modify the above answers and do something like this... (where Details is the Action method name on the controller)

 var fakeRequest = Substitute.For<HttpRequestBase>();
 var fakeContext = Substitute.For<HttpContextBase>();
 fakeRequest.Headers.Returns(new WebHeaderCollection { {"X-Requested-With", "XMLHttpRequest"}});
 fakeContext.Request.Returns(fakeRequest);
 controller.ControllerContext = new ControllerContext(fakeContext, new RouteData(), controller);
 var model = new EntityTypeMaintenanceModel();
        
 var result = controller.Details(model) as PartialViewResult;
        
 Assert.IsNotNull(result);
 Assert.AreEqual("EntityType", result.ViewName);

Here is a working solution using RhinoMocks. I've based it on a Moq solution I found at http://thegrayzone.co.uk/blog/2010/03/mocking-request-isajaxrequest/

public static void MakeAjaxRequest(this Controller controller)
{
        MockRepository mocks = new MockRepository();

        // Create mocks
        var mockedhttpContext = mocks.DynamicMock<HttpContextBase>();
        var mockedHttpRequest = mocks.DynamicMock<HttpRequestBase>();

        // Set headers to pretend it's an Ajax request
        SetupResult.For(mockedHttpRequest.Headers)
            .Return(new WebHeaderCollection() {
                {"X-Requested-With", "XMLHttpRequest"}
            });

        // Tell the mocked context to return the mocked request
        SetupResult.For(mockedhttpContext.Request).Return(mockedHttpRequest);

        mocks.ReplayAll();

        // Set controllerContext
        controller.ControllerContext = new ControllerContext(mockedhttpContext, new RouteData(), controller);
}

Is AjaxRequest is an extension method. So you can do it the following way using Rhino:

    protected HttpContextBase BuildHttpContextStub(bool isAjaxRequest)
    {
        var httpRequestBase = MockRepository.GenerateStub<HttpRequestBase>();   
        if (isAjaxRequest)
        {
            httpRequestBase.Stub(r => r["X-Requested-With"]).Return("XMLHttpRequest");
        }

        var httpContextBase = MockRepository.GenerateStub<HttpContextBase>();
        httpContextBase.Stub(c => c.Request).Return(httpRequestBase);

        return httpContextBase;
    }

    // Build controller
    ....
    controller.ControllerContext = new ControllerContext(BuildHttpContextStub(true), new RouteData(), controller);

Looks like you are looking for this,

 var requestMock = new Mock<HttpRequestBase>();
 requestMock.SetupGet(rq => rq["Age"]).Returns("2001");

Usage in Controller :

 public ActionResult Index()
 {
        var age = Request["Age"]; //This will return 2001
 }

You need to mock HttpContextBase and put it into your ControllerContext property, like that:

controller.ControllerContext = 
new ControllerContext(mockedHttpContext, new RouteData(), controller);

In current .NET (v 5):

var controller = new SomeController(); // SomeController that inherits Microsoft.AspNetCore.Mvc.ControllerBase
var httpContext = new DefaultHttpContext(); // DefaultHttpContext class is part of Microsoft.AspNetCore.Http namespace
httpContext.Request.Headers.Add("origin", "0.0.0.1"); // Add your custom headers to request
controller.ControllerContext.HttpContext = httpContext;

To make IsAjaxRequest() to return false during Unit test you need to setup Request Headers as well as request collection value both in your test method as given below:

_request.SetupGet(x => x.Headers).Returns(new System.Net.WebHeaderCollection { { "X-Requested-With", "NotAjaxRequest" } });
_request.SetupGet(x=>x["X-Requested-With"]).Returns("NotAjaxRequest");

The reason for setting up both is hidden in implementation of IsAjaxRequest() which is given below:

public static bool IsAjaxRequest(this HttpRequestBase request)<br/>
{ 
    if (request == null)
    {
        throw new ArgumentNullException("request");
    }
    return ((request["X-Requested-With"] == "XMLHttpRequest") || ((request.Headers != null) && (request.Headers["X-Requested-With"] == "XMLHttpRequest")));
}

It uses both request Collection and header this is why we need to create setup for both Header and Request Collection.

this will make the request to return false when it is not a ajax request. to make it return true you can do the following:

_httpContext.SetupGet(x => x.Request["X-Requested-With"]).Returns("XMLHttpRequest");

I found other way to add a HttpRequestMessage object into your request during Web API as follow

[Test]
public void TestMethod()
{
    var controllerContext = new HttpControllerContext();
    var request = new HttpRequestMessage();
    request.Headers.Add("TestHeader", "TestHeader");
    controllerContext.Request = request;
    _controller.ControllerContext = controllerContext;

    var result = _controller.YourAPIMethod();
    //Your assertion
}

(A bit late to the party but I went for a different route so thought I'd share)

To go for a pure code/mocking way of testing this without creating mocks for Http classes I implemented an IControllerHelper which has an Initialise method which takes the Request as a parameter and then exposed properties I want eg:

    public interface IControllerHelper
    {
        void Initialise(HttpRequest request);
        string HostAddress { get; }
    }

    public class ControllerHelper : IControllerHelper
    {
        private HttpRequest _request;
        
        public void Initialise(HttpRequest request)
        {
            _request = request;
        }

        public string HostAddress =>  _request.GetUri().GetLeftPart(UriPartial.Authority);
    }

Then in my controller I call initialise at the start of the method:

        _controllerHelper.Initialise(Request);

And then my code is only dependent on mockable dependacies.

        return Created(new Uri($"{_controllerHelper.HostName}/api/MyEndpoint/{result.id}"), result);

For functional tests I just override the iControllerHelper in the composition for a substitute.