Asp.net mvc 测试ActionMailer.Net.Mvc HttpContext为空

我正试图编写集成测试来测试我的Mailer类。此mailer类调用ActionMailer.Net.Mvc.MailerBase电子邮件方法来发送邮件。我已经在测试方法上设置了属性

[UrlToTest("http://localhost:8000/")] 

[HostType("ASP.NET")]

但我还是得到了以下例外

**System.ArgumentNullException was unhandled by user code
  HResult=-2147467261
  Message=Value cannot be null.
Parameter name: httpContext
  Source=System.Web
  ParamName=httpContext
  StackTrace:
       at System.Web.Routing.RequestContext..ctor(HttpContextBase httpContext, RouteData routeData)
       at ActionMailer.Net.Mvc.MailerBase.Email(String viewName, Object model, String masterName, Boolean trimBody) in c:\Dev\actionmailer\src\ActionMailer.Net.Mvc\MailerBase.cs:line 163
       at Shindigg.Services.Messaging.Mailer.OrderConfirmation(OrderConfirmationMessageModel orderConfirmationMessageModel) in D:\Projects\Shindig\main\Src\UltimateEvents\Shindigg.Services\Messaging\Mailer.cs:line 33
       at Shindigg.Services.Messaging.MessageService.SendOrderConfirmation(Order order, List`1 pdfTicketAttachments) in D:\Projects\Shindig\main\Src\UltimateEvents\Shindigg.Services\Messaging\MessageService.cs:line 78
       at UltimateEvents.WebSite.Controllers.TestController.TestMessage(Order order) in D:\Projects\Shindig\main\Src\UltimateEvents\UltimateEvents.WebSite\Controllers\TestController.cs:line 211
       at UltimateEvents.WebSite.Tests.MessageServiceTest.TestMessage() in D:\Projects\Shindig\main\Src\UltimateEvents\UltimateEvents.WebSite.Tests\MessageServiceTest.cs:line 56
  InnerException:**