如何模拟server.htmlencode

我正在尝试以下操作,但我正在获取:未将对象引用设置为对象的实例。

 HttpContextBase mockContext = MockRepository.GenerateMock<HttpContextBase>();

 mockContext.Expect(c => c.Server.HtmlEncode("")).IgnoreArguments().Return("");
 mockContext.Expect(c => c.Server.HtmlDecode("")).Return("");

 controller.ControllerContext = 
    new ControllerContext(mockContext, new RouteData(), controller);

马汀,

谢谢。这足以让我指向这里提供的正确方向:

var mockContext = MockRepository.GenerateMock<HttpContextBase>();       
var mockServer = MockRepository.GenerateMock<HttpServerUtilityBase>();

mockServer.Expect(s => s.HtmlEncode(""))
    .IgnoreArguments()
    .Repeat.AtLeastOnce()
    .Return("");

mockContext.Expect(c => c.Server)
    .IgnoreArguments()
    .Repeat.AtLeastOnce()
    .Return(mockServer);

controller.ControllerContext = 
    new ControllerContext(mockContext, new RouteData(), controller);