如何在单元测试中模拟控制器上下文，以便我对字符串函数的部分视图起作用？

我正在尝试为我的控制器创建一个单元测试，但是我正在测试的操作使用了字符串函数的部分视图，该函数不想在我的测试中工作。

private string RenderPartialViewToString(string viewName, object model = null)
{
   if (string.IsNullOrEmpty(viewName))
            viewName = ControllerContext.RouteData.GetRequiredString("action");

   ViewData.Model = model;

   using (System.IO.StringWriter sw = new System.IO.StringWriter())
   {
      ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
      ViewContext viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
      viewResult.View.Render(viewContext, sw);

      return sw.GetStringBuilder().ToString();
   }
}

这给了我一个错误“对象引用未设置到对象的实例”ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);

我在控制器单元测试中的设置是（删除了一些位以简化它）：

var mock = new Mock<ControllerContext>();
mock.SetupGet(p => p.HttpContext.User.Identity.Name).Returns(userName);
if (userName != null)
{
   mock.SetupGet(p => p.HttpContext.Request.IsAuthenticated).Returns(true);
   mock.SetupGet(p => p.HttpContext.User.Identity.IsAuthenticated).Returns(true);
}
else
{
   mock.SetupGet(p => p.HttpContext.Request.IsAuthenticated).Returns(false);
}
var controller = new BlogController();
controller.ControllerContext = mock.Object;

我没有运气尝试找到解决方案或解决方法。任何帮助表示赞赏。谢谢。

正如所建议的，我已尝试设置路线数据，但仍然收到错误。这是我添加的内容：

var routeData = new RouteData();
routeData.Values.Add("controller", "BlogController");
mock.SetupGet(m => m.RouteData).Returns(routeData);

最终解决方案感谢评论中的帮助。

var mock = new Mock<ControllerContext>();
mock.SetupGet(p => p.HttpContext.User.Identity.Name).Returns(userName);
if (userName != null)
{
   mock.SetupGet(p => p.HttpContext.Request.IsAuthenticated).Returns(true);
   mock.SetupGet(p => p.HttpContext.User.Identity.IsAuthenticated).Returns(true);
}
else
{
   mock.SetupGet(p => p.HttpContext.Request.IsAuthenticated).Returns(false);
}

var routeData = new RouteData();
routeData.Values.Add("controller", "BlogController");
mock.SetupGet(m => m.RouteData).Returns(routeData);

var view = new Mock<IView>();
var engine = new Mock<IViewEngine>();
var viewEngineResult = new ViewEngineResult(view.Object, engine.Object);
engine.Setup(e => e.FindPartialView(It.IsAny<ControllerContext>(), It.IsAny<string>(), It.IsAny<bool>())).Returns(viewEngineResult);
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(engine.Object);

var controller = new BlogController();
controller.ControllerContext = mock.Object;