ASP.NET MVC 5: Testable RouteCollection.MapMvcAttributeRoutes

MapMvcAttributeRoutes.Testable.cs

public static void MapMvcAttributeRoutes(
    this RouteCollection routeCollection,
    Assembly controllerAssembly,
    IInlineConstraintResolver constraintResolver = null)
{
    var controllerTypes = (from type in controllerAssembly.GetExportedTypes()
                            where
                                type != null && type.IsPublic
                                && type.Name.EndsWith("Controller", StringComparison.OrdinalIgnoreCase)
                                && !type.IsAbstract && typeof(IController).IsAssignableFrom(type)
                            select type).ToList();

    var attributeRoutingAssembly = typeof(RouteCollectionAttributeRoutingExtensions).Assembly;
    var attributeRoutingMapperType =
        attributeRoutingAssembly.GetType("System.Web.Mvc.Routing.AttributeRoutingMapper");

    var mapAttributeRoutesMethod = attributeRoutingMapperType.GetMethod(
        "MapAttributeRoutes",
        BindingFlags.Public | BindingFlags.Static,
        null,
        new[] { typeof(RouteCollection), typeof(IEnumerable<Type>), typeof(IInlineConstraintResolver) },
        null);

    constraintResolver = constraintResolver ?? new DefaultInlineConstraintResolver();
    mapAttributeRoutesMethod.Invoke(null, new object[] { routeCollection, controllerTypes, constraintResolver });
}