代码之家 › 专栏 › 技术社区 › Rob Cooper

从WebRequest模拟WebResponse

webresponse webrequest rest web-services xml

Rob Cooper · 技术社区 · 17 年前

我终于开始费劲地创建一些与RESTful Web界面一起工作的应用程序,但是,我担心每次我点击F5运行一系列测试时,我都会敲打它们的服务器。

基本上,我需要得到一系列的Web响应,这样我就可以测试我是否正确地解析不同的响应,而不是每次都访问它们的服务器,我认为我可以这样做一次,保存XML,然后在本地工作。

但是,我不知道如何“模拟”Web响应,因为(afaik)它们只能由 Web请求.getResponse

你们怎么嘲笑这种事?你…吗?我只是真的不喜欢我锤击他们的服务器:s我不想更改代码太很多,但我希望有一种优雅的方式来做到这一点。

接受后更新

威尔的回答是打我需要的脸,我知道我错过了一个基本点!

创建一个将返回代表XML的代理对象的接口。
实现接口两次,一次使用WebRequest,另一次返回静态“响应”。
然后,接口实现或者根据响应实例化返回类型,或者静态XML。
然后,您可以在测试或生产时将所需的类传递给服务层。

一旦我把代码整理好,我就粘贴一些样本。

5 回复 | 直到 17 年前

Despertar 12 年前

我在做完全相同的事情时发现了这个问题。在任何地方都找不到答案,但经过一番挖掘,发现.NET框架内置了对此的支持。

可以用注册工厂对象 WebRequest.RegisterPrefix 哪一个 WebRequest.Create 使用该前缀(或URL)时将调用。工厂对象必须实现 IWebRequestCreate 只有一种方法 Create 返回一个 WebRequest . 在这里你可以退回你的模型 WebREST .

我把一些示例代码放在 http://blog.salamandersoft.co.uk/index.php/2009/10/how-to-mock-httpwebrequest-when-unit-testing/

escape-llc 13 年前

这里有一个不需要模拟的解决方案。您可以实现 WebRequest : IWebRequestCreate WebREST 和 WebResponse . 见下文。我的示例生成失败的请求(通过抛出 WebException ,但应能使其适应发送“真实”响应:

class WebRequestFailedCreate : IWebRequestCreate {
    HttpStatusCode status;
    String statusDescription;
    public WebRequestFailedCreate(HttpStatusCode hsc, String sd) {
        status = hsc;
        statusDescription = sd;
    }
    #region IWebRequestCreate Members
    public WebRequest Create(Uri uri) {
        return new WebRequestFailed(uri, status, statusDescription);
    }
    #endregion
}
class WebRequestFailed : WebRequest {
    HttpStatusCode status;
    String statusDescription;
    Uri itemUri;
    public WebRequestFailed(Uri uri, HttpStatusCode status, String statusDescription) {
        this.itemUri = uri;
        this.status = status;
        this.statusDescription = statusDescription;
    }
    WebException GetException() {
        SerializationInfo si = new SerializationInfo(typeof(HttpWebResponse), new System.Runtime.Serialization.FormatterConverter());
        StreamingContext sc = new StreamingContext();
        WebHeaderCollection headers = new WebHeaderCollection();
        si.AddValue("m_HttpResponseHeaders", headers);
        si.AddValue("m_Uri", itemUri);
        si.AddValue("m_Certificate", null);
        si.AddValue("m_Version", HttpVersion.Version11);
        si.AddValue("m_StatusCode", status);
        si.AddValue("m_ContentLength", 0);
        si.AddValue("m_Verb", "GET");
        si.AddValue("m_StatusDescription", statusDescription);
        si.AddValue("m_MediaType", null);
        WebResponseFailed wr = new WebResponseFailed(si, sc);
        Exception inner = new Exception(statusDescription);
        return new WebException("This request failed", inner, WebExceptionStatus.ProtocolError, wr);
    }
    public override WebResponse GetResponse() {
        throw GetException();
    }
    public override IAsyncResult BeginGetResponse(AsyncCallback callback, object state) {
        Task<WebResponse> f = Task<WebResponse>.Factory.StartNew (
            _ =>
            {
                throw GetException();
            },
            state
        );
        if (callback != null) f.ContinueWith((res) => callback(f));
        return f;
    }
    public override WebResponse EndGetResponse(IAsyncResult asyncResult) {
        return ((Task<WebResponse>)asyncResult).Result;
    }

}
class WebResponseFailed : HttpWebResponse {
    public WebResponseFailed(SerializationInfo serializationInfo, StreamingContext streamingContext)
        : base(serializationInfo, streamingContext) {
    }
}

必须创建一个 HttpWebResponse 子类,因为您不能创建子类。

棘手的部分 GetException() 方法)正在输入不能重写的值,例如 StatusCode 这是我们最好的朋友 SerializaionInfo 进来!这是您提供不能重写的值的地方。显然,覆盖 HTTPWebRead )你能,把剩下的路开到那里。

我是如何获得所有这些“名字”的 AddValue() 电话?来自异常消息!我很高兴能依次告诉我每一件事,直到我让它高兴为止。

现在,编译器会抱怨“过时”,但这仍然有效,包括.NET框架版本4。

以下是一个(通过的)测试用例供参考:

    [TestMethod, ExpectedException(typeof(WebException))]
    public void WebRequestFailedThrowsWebException() {
        string TestURIProtocol = TestContext.TestName;
        var ResourcesBaseURL = TestURIProtocol + "://resources/";
        var ContainerBaseURL = ResourcesBaseURL + "container" + "/";
        WebRequest.RegisterPrefix(TestURIProtocol, new WebRequestFailedCreate(HttpStatusCode.InternalServerError, "This request failed on purpose."));
        WebRequest wr = WebRequest.Create(ContainerBaseURL);
        try {
            WebResponse wrsp = wr.GetResponse();
            using (wrsp) {
                Assert.Fail("WebRequest.GetResponse() Should not have succeeded.");
            }
        }
        catch (WebException we) {
            Assert.IsInstanceOfType(we.Response, typeof(HttpWebResponse));
            Assert.AreEqual(HttpStatusCode.InternalServerError, (we.Response as HttpWebResponse).StatusCode, "Status Code failed");
            throw we;
        }
    }

Will 16 年前

你不能。最好把它包装在代理对象中,然后模仿它。或者,您必须使用一个模拟框架来拦截不能模拟的类型,比如typemock。但你说的是美元。最好做一点包装。

很显然你可以有点额外的工作。在这里检查投票最高的答案。

Simon Parsons 15 年前

我在前面找到了下面的博客,它解释了使用Microsoft Moles的非常好的方法。

http://maraboustork.co.uk/index.php/2011/03/mocking-httpwebresponse-with-moles/

简而言之,解决方案建议如下:

    [TestMethod]
    [HostType("Moles")]
    [Description("Tests that the default scraper returns the correct result")]
    public void Scrape_KnownUrl_ReturnsExpectedValue()
    {
        var mockedWebResponse = new MHttpWebResponse();

        MHttpWebRequest.AllInstances.GetResponse = (x) =>
        {
            return mockedWebResponse;
        };

        mockedWebResponse.StatusCodeGet = () => { return HttpStatusCode.OK; };
        mockedWebResponse.ResponseUriGet = () => { return new Uri("http://www.google.co.uk/someRedirect.aspx"); };
        mockedWebResponse.ContentTypeGet = () => { return "testHttpResponse"; }; 

        var mockedResponse = "<html> \r\n" +
                             "  <head></head> \r\n" +
                             "  <body> \r\n" +
                             "     <h1>Hello World</h1> \r\n" +
                             "  </body> \r\n" +
                             "</html>";

        var s = new MemoryStream();
        var sw = new StreamWriter(s);

            sw.Write(mockedResponse);
            sw.Flush();

            s.Seek(0, SeekOrigin.Begin);

        mockedWebResponse.GetResponseStream = () => s;

        var scraper = new DefaultScraper();
        var retVal = scraper.Scrape("http://www.google.co.uk");

        Assert.AreEqual(mockedResponse, retVal.Content, "Should have returned the test html response");
        Assert.AreEqual("http://www.google.co.uk/someRedirect.aspx", retVal.FinalUrl, "The finalUrl does not correctly represent the redirection that took place.");
    }

dr. evil 17 年前

这不是一个完美的解决方案,但它以前对我很有效,应该特别注意简单性:

HTTPSimulator

另外还有一个typemock示例,记录在 typemock forums :

using System;
using System.IO;
using System.Net;
using NUnit.Framework;
using TypeMock;

namespace MockHttpWebRequest
{
  public class LibraryClass
  {
    public string GetGoogleHomePage()
    {
      HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://www.google.com");
      HttpWebResponse response = (HttpWebResponse)request.GetResponse();
      using (StreamReader reader = new StreamReader(response.GetResponseStream()))
      {
        return reader.ReadToEnd();
      }
    }
  }

  [TestFixture]
  [VerifyMocks]
  public class UnitTests
  {
    private Stream responseStream = null;
    private const string ExpectedResponseContent = "Content from mocked response.";

    [SetUp]
    public void SetUp()
    {
      System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
      byte[] contentAsBytes = encoding.GetBytes(ExpectedResponseContent);
      this.responseStream = new MemoryStream();
      this.responseStream.Write(contentAsBytes, 0, contentAsBytes.Length);
      this.responseStream.Position = 0;
    }

    [TearDown]
    public void TearDown()
    {
      if (responseStream != null)
      {
        responseStream.Dispose();
        responseStream = null;
      }
    }

    [Test(Description = "Mocks a web request using natural mocks.")]
    public void NaturalMocks()
    {
      HttpWebRequest mockRequest = RecorderManager.CreateMockedObject<HttpWebRequest>(Constructor.Mocked);
      HttpWebResponse mockResponse = RecorderManager.CreateMockedObject<HttpWebResponse>(Constructor.Mocked);
      using (RecordExpectations recorder = RecorderManager.StartRecording())
      {
        WebRequest.Create("http://www.google.com");
        recorder.CheckArguments();
        recorder.Return(mockRequest);

        mockRequest.GetResponse();
        recorder.Return(mockResponse);

        mockResponse.GetResponseStream();
        recorder.Return(this.responseStream);
      }

      LibraryClass testObject = new LibraryClass();
      string result = testObject.GetGoogleHomePage();
      Assert.AreEqual(ExpectedResponseContent, result);
    }

    [Test(Description = "Mocks a web request using reflective mocks.")]
    public void ReflectiveMocks()
    {
      Mock<HttpWebRequest> mockRequest = MockManager.Mock<HttpWebRequest>(Constructor.Mocked);
      MockObject<HttpWebResponse> mockResponse = MockManager.MockObject<HttpWebResponse>(Constructor.Mocked);
      mockResponse.ExpectAndReturn("GetResponseStream", this.responseStream);
      mockRequest.ExpectAndReturn("GetResponse", mockResponse.Object);

      LibraryClass testObject = new LibraryClass();
      string result = testObject.GetGoogleHomePage();
      Assert.AreEqual(ExpectedResponseContent, result);
    }
  }
}