无法从httpContextBase转换为httpContextBase

使用以下代码(使用MOQ 4.0.10501.6):

HomeController controller = new HomeController();
ActionResult result = _controller.Index();

Mock<HttpResponseBase> response = new Mock<HttpResponseBase>();

Mock<HttpContextBase> httpContext = new Mock<HttpContextBase>();
httpContext.Setup(x => x.Response).Returns(response.Object);

Mock<ControllerContext> controllerContext = new Mock<ControllerContext>();
controllerContext.Setup(c => c.HttpContext).Returns(httpContext.Object);
result.ExecuteResult(controllerContext.Object);

…我得到以下编译器错误:

error CS1502: The best overloaded method match for
'Moq.Language.IReturns<System.Web.Mvc.ControllerContext,
 System.Web.HttpContextBase>.Returns(System.Web.HttpContextBase)'
has some invalid arguments

error CS1503: Argument 1: cannot convert from 'System.Web.HttpContextBase
[c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\
v4.0\System.Web.dll]' to 'System.Web.HttpContextBase'

我做错了什么?为什么我不能从 HttpContextBase 到 HTTPTCP数据库 ?

我从一个ASP.NET MVC项目开始,添加了一个nunit测试项目,并重新分析了缺少的system.web引用。根据vs中的属性窗口,我引用的system.web.dll是 C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.Web.dll .