asp.net-mvc – HttpContext和HttpContextWrapper之间的区别在单

I heard that it’s useful in Unit Testing in comparing with Web Forms. but how it’s useful ?

我们举一个ASP.NET MVC控制器操作的例子，该操作向响应添加一个cookie：

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var cookie = new HttpCookie("foo","bar");
        this.Response.Cookies.Add(cookie);
        return View();
    }
}

注意那里的Response属性。这是一个HttpResponseBase。所以我们可以在单元测试中模拟它：

public class HttpResponseMock: HttpResponseBase
{
    private HttpCookieCollection cookies;
    public override HttpCookieCollection Cookies
    {
        get
        {
            if (this.cookies == null)
            {
                this.cookies = new HttpCookieCollection();
            }

            return this.cookies;
        }
    }
}

public class HttpContextMock: HttpContextBase
{
    private HttpResponseBase response;

    public override HttpResponseBase Response
    {
        get 
        {
            if (this.response == null)
            {
                this.response = new HttpResponseMock();
            }
            return this.response;
        }
    }
}

现在我们可以写一个单元测试：

// arrange
var sut = new HomeController();
var httpContext = new HttpContextMock();
sut.ControllerContext = new ControllerContext(httpContext,new RouteData(),sut);

// act
var actual = sut.Index();

// assert
Assert.AreEqual("bar",sut.Response.Cookies["foo"].Value);

由于所有成员都是虚拟的，我们可以使用一个嘲笑的框架，这将避免我们将这些模拟类写入单元测试。例如，NSubstitute这里是测试的样子：

// arrange
var sut = new HomeController();
var context = Substitute.For<HttpContextBase>();
var response = Substitute.For<HttpResponseBase>();
var cookies = new HttpCookieCollection();
context.Response.Returns(response);
context.Response.Cookies.Returns(cookies);
sut.ControllerContext = new ControllerContext(context,sut.Response.Cookies["foo"].Value);

现在我们来一个WebForm：

protected void Page_Load(object sender,EventArgs)
{
    var cookie = new HttpCookie("foo","bar");
    this.Response.Cookies.Add(cookie);
}

在这种情况下，Response属性是具体的HttpResponse。所以你被打倒了不可能单独测试。