找不到API路由

我的代码中有一个带有路由前缀的API,但是当我尝试去访问它时,我得到了404。这是我的代码:

namespace MyProject.Authentication.Controllers
{
    [RoutePrefix("api/user")]
    public class MyUserController : ApiController
    {
        private readonly IMyDomainService _myDomainService;

        public MyUserController()
        {
            _myDomainService = new MyDomainService();
        }

        [HttpGet]
        [HttpRoute("get/test")]
        public HttpResponseMessage Test()
        {
            return Request.CreateResponse(HttpStatusCode.OK, "test success");
        }
    }
}

public static class AttributeRoutingHttpConfig
{
    public static void RegisterRoutes(HttpRouteCollection routes)
    {
        // See http://github.com/mccalltd/AttributeRouting/wiki for more options.
        // To debug routes locally using the built in ASP.NET development server, go to /routes.axd

        routes.MapHttpAttributeRoutes();
    }

    public static void Start()
    {
        RegisterRoutes(GlobalConfiguration.Configuration.Routes);
    }
}

编辑:这里是ASP.NET4.5