The Test Helpers are a great way to ease your testing needs with MVC.  If your using the Test Helpers to test your routing like so:

            "~/".ShouldMapTo<HomeController>(x => x.Index());

When you run your tests you’ll get the following error:

System.Security.VerificationException : Method MvcContrib.TestHelper.RouteTestingExtensions.ShouldMapTo: type argument 'Your Controller Name’ violates the constraint of type parameter 'TController'.

The fix is a binding direct.

Add an app.config to your test project and paste in the following:

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
            <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
            <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="4.0.0.0" />
        </dependentAssembly>
    </assemblyBinding>
</runtime>

Happy Coding!