Episerver - minimal admin plugin

InitModule.cs

using System.Web.Mvc;
using System.Web.Routing;
using EPiServer.Framework;
using EPiServer.Framework.Initialization;

namespace Sandbox.CMS.Plugins
{
  public class InitModule : IInitializableModule
  {
    public void Initialize(InitializationEngine context)
    {
      // Add support for attribute routing
      RouteTable.Routes.MapMvcAttributeRoutes();
    }

    public void Uninitialize(InitializationEngine context)
    {
    }
  }
}

MyTestController.cs

using System.Web.Mvc;
using EPiServer.PlugIn;

namespace Sandbox.CMS.Plugins
{
  [GuiPlugIn(
    Area = PlugInArea.AdminMenu,
    Url = "/" + MyTestControllerPath,
    DisplayName = "My Plugin")]
  [Authorize(Roles = "CmsAdmins")]
  [Route(MyTestControllerPath)]
  public class MyTestController : Controller
  {
    internal const string MyTestControllerPath = "custom-plugins/my-plugin";

    public ActionResult Index()
    {
      return Content("Found");
    }
  }
}