Ever faced this situation: You have nice and easy controller method, say:

public ActionResult Demonstrate(string id) {
    this.Repository.Demonstrate(id);
    string url = this.Url.Action(MVC.Errors.Suck(id));
    return this.Redirect(url);
}

Then you go and create test for it (or created the test before, whatever suits you):

[TestMethod]
public void Demonstrate_ValidInput_Redirects()
{
    // Arrange
    var controller = new MyDemonstratingController();

    // ... mock something here

    // Act
    controller.Demonstrate("kaboom");

    // Assert
    // ... test that everything was called
}

…only to get NullReferenceException, since you did not set everything up that is needed by the UrlHelper class (controller’s Url property).

To satisfy the basic dependencies for a controller you can use MvcContrib’s TestControllerBuilder class like this:

TestControllerBuilder builder = new TestControllerBuilder();
builder.InitializeController(controller);

InitializeController method adds mock implementations of the following:

• HttpContext
• HttpRequest
• HttpResponse
• HttpSession
• Form
• TempData
• QueryString
• ApplicationPath
• PathInfo

There are also other helper methods than InitializeController in TestControllerBuilder, but for me InitializeController has been the most useful method from that library so far.