c# - 使用最小起订量模拟 HttpContext.Current.Server.MapPath？

Question

我正在对我的家庭 Controller 进行单元测试。在我添加保存图像的新功能之前，此测试运行良好。

导致问题的方法如下所示。

    public static void SaveStarCarCAPImage(int capID)
    {
        byte[] capBinary = Motorpoint2011Data.RetrieveCapImageData(capID);

        if (capBinary != null)
        {
            MemoryStream ioStream = new MemoryStream();
            ioStream = new MemoryStream(capBinary);

            // save the memory stream as an image
            // Read in the data but do not close, before using the stream.

            using (Stream originalBinaryDataStream = ioStream)
            {
                var path = HttpContext.Current.Server.MapPath("/StarVehiclesImages");
                path = System.IO.Path.Combine(path, capID + ".jpg");
                Image image = Image.FromStream(originalBinaryDataStream);
                Image resize = image.GetThumbnailImage(500, 375, null, new IntPtr());
                resize.Save(path, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
        }
    }

由于调用来自单元测试，因此 HttpContext.Current 为 null 并引发异常。在阅读了 Moq 和一些关于在 session 中使用 Moq 的教程后，我确信它可以完成。

到目前为止，单元测试代码已经出来了，但问题是 HTTPContext.Current 始终为 null，并且仍然抛出异常。

    protected ControllerContext CreateStubControllerContext(Controller controller)
    {
        var httpContextStub = new Mock<HttpContextBase>
        {
            DefaultValue = DefaultValue.Mock
        };

        return new ControllerContext(httpContextStub.Object, new RouteData(), controller);
    }

    [TestMethod]
    public void Index()
    {
        // Arrange
        HomeController controller = new HomeController();            
        controller.SetFakeControllerContext();

        var context = controller.HttpContext;

        Mock.Get(context).Setup(s => s.Server.MapPath("/StarVehiclesImages")).Returns("My Path");

        // Act
        ViewResult result = controller.Index() as ViewResult;

        // Assert
        HomePageModel model = (HomePageModel)result.Model;
        Assert.AreEqual("Welcome to ASP.NET MVC!", model.Message);
        Assert.AreEqual(typeof(List<Vehicle>), model.VehicleMakes.GetType());
        Assert.IsTrue(model.VehicleMakes.Exists(x => x.Make.Trim().Equals("Ford", StringComparison.OrdinalIgnoreCase)));
    }

Answer 1

HttpContext.Current 如果您希望对代码进行单元测试，则绝对不要使用它。它是一个静态方法，如果没有 Web 上下文(这是单元测试的情况并且不能被模拟)，它只会返回 null。因此，重构代码的一种方法如下:

public static void SaveStarCarCAPImage(int capID, string path)
{
    byte[] capBinary = Motorpoint2011Data.RetrieveCapImageData(capID, path);

    if (capBinary != null)
    {
        MemoryStream ioStream = new MemoryStream();
        ioStream = new MemoryStream(capBinary);

        // save the memory stream as an image
        // Read in the data but do not close, before using the stream.

        using (Stream originalBinaryDataStream = ioStream)
        {
            path = System.IO.Path.Combine(path, capID + ".jpg");
            Image image = Image.FromStream(originalBinaryDataStream);
            Image resize = image.GetThumbnailImage(500, 375, null, new IntPtr());
            resize.Save(path, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}

你看，现在这个方法不再依赖于任何网络上下文，可以单独测试了。调用者有责任传递正确的路径。