从 WebRequest 模拟 WebResponse
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01-07-2019 - |
题
我终于开始尝试创建一些与 RESTful Web 界面配合使用的应用程序,但是,我担心每次按 F5 运行一系列测试时我都会敲击他们的服务器。
基本上,我需要获得一系列网络响应,以便我可以测试我是否正确解析不同的响应,而不是每次都访问他们的服务器,我想我可以这样做一次,保存 XML,然后在本地工作。
但是,我不知道如何“模拟”WebResponse,因为(AFAIK)它们只能通过实例化 WebRequest.GetResponse
你们怎么会嘲笑这种事情呢?你?我只是真的不喜欢我敲打他们的服务器:S 我不想更改代码 也 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
威尔的回答是我需要的一记耳光,我知道我错过了一个基本点!
- 创建一个接口,该接口将返回代表 XML 的代理对象。
- 实现该接口两次,一次使用 WebRequest,另一次返回静态“响应”。
- 然后,接口实现要么根据响应实例化返回类型,要么实例化静态 XML。
- 然后,您可以在测试或生产时将所需的类传递到服务层。
一旦我敲定了代码,我就会粘贴一些示例。
解决方案
我在想做同样的事情时发现了这个问题。在任何地方都找不到答案,但经过更多挖掘后发现.Net Framework 已经内置了对此的支持。
您可以使用以下方式注册工厂对象 WebRequest.RegisterPrefix
哪个 WebRequest.Create
使用该前缀(或 url)时将调用。工厂对象必须实现 IWebRequestCreate
它只有一个方法 Create
它返回一个 WebRequest
. 。在这里你可以返回你的模拟 WebRequest
.
我已经将一些示例代码放在http://blog.salamandersoft.co.uk/index.php/2009/10/how-to-mock-httpwebrequest-when-unit-testing/
其他提示
这是一个不需要模拟的解决方案。您实现了所有三个组件 WebRequest
: IWebRequestCreate
WebRequest
和 WebResponse
. 。见下文。我的示例生成失败的请求(通过抛出 WebException
),但应该能够调整它以发送“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) {
}
}
您必须创建一个 HttpWebResponse
子类,因为您无法以其他方式创建子类。
棘手的部分(在 GetException()
方法)正在输入您无法覆盖的值,例如 StatusCode
这就是我们最好的朋友的地方 SerializaionInfo
进来!您可以在此处提供无法覆盖的值。显然,覆盖部分( HttpWebResponse
)你有能力完成剩下的事情。
我是如何获得所有这些中的“名字”的 AddValue()
打电话?来自异常消息!它很乐意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“已过时”,但这仍然有效,包括 .NET Framework 版本 4。
这是一个(通过)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;
}
}
你不能。最好的办法是将其包装在代理对象中,然后模拟它。或者,您必须使用可以拦截无法模拟的类型的模拟框架,例如 TypeMock。但你说的是钱。最好做一点包装。
显然你 能 需要一点额外的工作。在这里查看得票最高的答案。
我之前发现了以下博客,其中解释了使用 Microsoft Moles 的相当不错的方法。
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.");
}
这不是一个完美的解决方案,但它以前对我有用,并且值得额外注意它的简单性:
还有一个 typemock 示例记录在 类型模拟论坛:
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);
}
}
}