testable_url_helper.cs

For<UrlHelper>()
  .HybridHttpOrThreadLocalScoped()
  .Use(ctx =>
    {
      var httpContext = new HttpContextWrapper(HttpContext.Current);
      var routeData = RouteTable.Routes.GetRouteData(httpContext);
      return new UrlHelper(new RequestContext(httpContext, routeData));
    });

For<IUrlHelper>()
  .HybridHttpOrThreadLocalScoped()
  .Use(ctx => new MvcUrlHelper(ctx.GetInstance<UrlHelper>()));