Casting ActionResult as HttpNotFoundResult返回null

Question

我有一個單元測試我的控制器，斷言當找不到模型的實例時返回HttpNotFoundResult。問題是，控制器中的實際代碼按預期工作，但我的單元測試不是。將ActionResult轉換爲HttpNotFoundResult時，它返回null，因此我的單元測試失敗。

控制器代碼：

public ActionResult Delete(int? id) 
     { 
      if(id == null) 
      { 
       return new HttpStatusCodeResult(HttpStatusCode.BadRequest); 
      } 
      Forum forum = forumRepository.GetForumById(id.GetValueOrDefault()); 
      if(forum == null) 
      { 
       return new HttpStatusCodeResult(HttpStatusCode.NotFound); 
      } 
      return View(forum); 
     } 

試驗方法：

[TestMethod] 
     public void GetDeleteShouldReturn404IfForumNotFound() 
     { 
      // Arrange 
      var forumRepository = Mock.Create<IForumRepository>(); 
      Mock.Arrange(() => forumRepository.GetForums()) 
       .Returns(new List<Forum>() { 
        new Forum { ForumId = 1, Title = "General Forum", Description = "Place to discuss general stuff", Sequence = 2 }, 
        new Forum { ForumId = 2, Title = "Gaming", Description = "Let's talk about gaming", Sequence = 1 }, 
        new Forum { ForumId = 3, Title = "Web Development", Description = "ASP.NET is pretty cool", Sequence = 3 } 
       }).MustBeCalled(); 

      // Act 
      ForumController controller = new ForumController(forumRepository); 
      ActionResult result = controller.Delete(5) as HttpNotFoundResult; 

      // Assert 
      Assert.IsNotNull(result); 
      Assert.IsInstanceOfType(result, typeof(HttpNotFoundResult)); 
     } 

的Assert.IsNotNull失敗。我也曾嘗試用相同的結果如下：

HttpNotFoundResult result = controller.Delete(5) as HttpNotFoundResult; 

這博格爾斯我的腦海裏，因爲我已經在幾個例子幾乎相同的代碼所示：

http://weblogs.asp.net/gunnarpeipman/archive/2010/08/15/asp-net-mvc-3-using-httpnotfoundresult-in-controller-tests.aspx

有什麼我做錯了？

編輯：

的問題是，我是不是嘲笑GetForumById（），改變測試代碼以下工作：

[TestMethod] 
     public void GetDeleteShouldReturn404IfForumNotFound() 
     { 
      // Arrange 
      var id = 10; 
      Forum forum = null; 

      var forumRepository = Mock.Create<IForumRepository>(); 

      Mock.Arrange(() => forumRepository.GetForumById(id)) 
       .Returns(forum) 
       .MustBeCalled(); 

      // Act 
      ForumController controller = new ForumController(forumRepository); 
      var result = controller.Delete(id) as HttpNotFoundResult; 

      // Assert 
      Assert.IsNotNull(result); 
      Assert.IsInstanceOfType(result, typeof(HttpNotFoundResult)); 
     } 

Answer 1

這是因爲HttpNotFoundResult從HttpStatusCodeResult派生，而不是周圍的其他方法。你正在使一個無效的downcast，這使得as語句返回null。