ASP.NET MVC: Unit testing controllers that use UrlHelper

One of my controllers actions, one that is being called in an Ajax request, is returning an URL to the client side so it can do a redirection. I'm using Url.RouteUrl(..) and during my unit tests this fails since the Controller.Url parameter is not pre-filled.

I tried a lot of things, among others attempting to stub UrlHelper (which failed), manually creating a UrlHelper with a RequestContext that has a stubbed HttpContextBase (which failed on a RouteCollection.GetUrlWithApplicationPath call).

I have searched Google but found virtually nothing on the subject. Am I doing something incredibly stupid using Url.RouteUrl in my Controller action? Is there an easier way?

To make it even worse, I'd like to be able to test the returned URL in my unit test - in fact I'm only interested in knowing it's redirecting to the right route, but since I'm returning an URL instead of a route, I would like to control the URL that is resolved (eg. by using a stubbed RouteCollection) - but I'll be happy to get my test passing to begin with.

Here is one of my tests (xUnit + Moq) just for similar case (using Url.RouteUrl in controller)

Hope this helps:

var routes = new RouteCollection();
MvcApplication.RegisterRoutes(routes);

var request = new Mock<HttpRequestBase>(MockBehavior.Strict);
request.SetupGet(x => x.ApplicationPath).Returns("/");
request.SetupGet(x => x.Url).Returns(new Uri("http://localhost/a", UriKind.Absolute));
request.SetupGet(x => x.ServerVariables).Returns(new System.Collections.Specialized.NameValueCollection());

var response = new Mock<HttpResponseBase>(MockBehavior.Strict);
response.Setup(x => x.ApplyAppPathModifier("/post1")).Returns("http://localhost/post1");

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

var controller = new LinkbackController(dbF.Object);
controller.ControllerContext = new ControllerContext(context.Object, new RouteData(), controller);
controller.Url = new UrlHelper(new RequestContext(context.Object, new RouteData()), routes);

A modified implementation from eu-ge-ne. This one returns a generated link based on the routes defined in the application. eu-ge-ne's example always returned a fixed response. The approach below will allow you to test that the correct action/controller and route information is being passed into the UrlHelper - which is what you want if you are testing call to the UrlHelper.

var context = new Mock<HttpContextBase>();
var request = new Mock<HttpRequestBase>();
var response = new Mock<HttpResponseBase>();
var session = new Mock<HttpSessionStateBase>();
var server = new Mock<HttpServerUtilityBase>();

context.Setup(ctx => ctx.Request).Returns(request.Object);
context.Setup(ctx => ctx.Response).Returns(response.Object);
context.Setup(ctx => ctx.Session).Returns(session.Object);
context.Setup(ctx => ctx.Server).Returns(server.Object);

request.SetupGet(x => x.ApplicationPath).Returns("/");
request.SetupGet(x => x.Url).Returns(new Uri("http://localhost/a", UriKind.Absolute));
request.SetupGet(x => x.ServerVariables).Returns(new NameValueCollection());

response.Setup(x => x.ApplyAppPathModifier(It.IsAny<string>())).Returns<string>(x => x);

context.SetupGet(x => x.Request).Returns(request.Object);
context.SetupGet(x => x.Response).Returns(response.Object);

var routes = new RouteCollection();
MvcApplication.RegisterRoutes(routes);
var helper = new UrlHelper(new RequestContext(context.Object, new RouteData()), routes);

This post may be useful if you want to mock HttpContextBase class.

http://www.hanselman.com/blog/ASPNETMVCSessionAtMix08TDDAndMvcMockHelpers.aspx

Building off the answer by @eu-ge-ne which helped me a great deal:

I had an ActionResult that did a redirect as well as had an UpdateModel call with a FormCollection parameter. For the UpdateModel() to work I had to add this to my Mocked HttpRequestBase:

FormCollection collection = new FormCollection();
collection["KeyName"] = "KeyValue";

request.Setup(x => x.Form).Returns(collection);
request.Setup(x => x.QueryString).Returns(new NameValueCollection());

To test that the redirected URL was correct, you can do the following:

RedirectResult result = controller.ActionName(modelToSubmit, collection) as RedirectResult;
Assert.AreEqual("/Expected/URL", result.Url);