我有一些问题，试图包装我的代码在单元测试中使用。问题在于。我有接口IHttpHandler:
public interface IHttpHandler
{
HttpClient client { get; }
}
使用它的类HttpHandler:
public class HttpHandler : IHttpHandler
{
public HttpClient client
{
get
{
return new HttpClient();
}
}
}
然后是Connection类，它使用simpleIOC注入客户端实现:
public class Connection
{
private IHttpHandler _httpClient;
public Connection(IHttpHandler httpClient)
{
_httpClient = httpClient;
}
}
然后我有一个单元测试项目，它有这个类:
private IHttpHandler _httpClient;
[TestMethod]
public void TestMockConnection()
{
var client = new Connection(_httpClient);
client.doSomething();
// Here I want to somehow create a mock instance of the http client
// Instead of the real one. How Should I approach this?
}
现在很明显，我将在Connection类中拥有从后端检索数据(JSON)的方法。但是，我想为这个类编写单元测试，显然我不想针对真正的后端编写测试，而是一个模拟的后端。我试着给这个问题一个好的答案，但没有成功。我以前可以用Moq来模拟，但从来没有在HttpClient这样的东西上使用过。我应该如何处理这个问题?
这是一个老问题，但我有一种冲动，想用一个我在这里没有看到的解决方案来扩展答案。
您可以伪造Microsoft程序集(System.Net.Http)，然后在测试期间使用ShinsContext。
In VS 2017, right click on the System.Net.Http assembly and choose "Add Fakes Assembly"
Put your code in the unit test method under a ShimsContext.Create() using. This way, you can isolate the code where you are planning to fake the HttpClient.
Depends on your implementation and test, I would suggest to implement all the desired acting where you call a method on the HttpClient and want to fake the returned value. Using ShimHttpClient.AllInstances will fake your implementation in all the instances created during your test. For example, if you want to fake the GetAsync() method, do the following:
[TestMethod]
public void FakeHttpClient()
{
using (ShimsContext.Create())
{
System.Net.Http.Fakes.ShimHttpClient.AllInstances.GetAsyncString = (c, requestUri) =>
{
//Return a service unavailable response
var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.ServiceUnavailable);
var task = Task.FromResult(httpResponseMessage);
return task;
};
//your implementation will use the fake method(s) automatically
var client = new Connection(_httpClient);
client.doSomething();
}
}
你所需要的只是传递给HttpClient ctor的HttpMessageHandler类的测试版本。主要的一点是，您的测试HttpMessageHandler类将有一个HttpRequestHandler委托，调用者可以设置它，并简单地以他们想要的方式处理HttpRequest。
public class FakeHttpMessageHandler : HttpMessageHandler
{
public Func<HttpRequestMessage, CancellationToken, HttpResponseMessage> HttpRequestHandler { get; set; } =
(r, c) =>
new HttpResponseMessage
{
ReasonPhrase = r.RequestUri.AbsoluteUri,
StatusCode = HttpStatusCode.OK
};
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
return Task.FromResult(HttpRequestHandler(request, cancellationToken));
}
}
您可以使用该类的实例来创建具体的HttpClient实例。通过HttpRequestHandler委托，你可以完全控制HttpClient发出的http请求。
也许在您当前的项目中会有一些代码需要更改，但对于新项目，您绝对应该考虑使用Flurl。
https://flurl.dev
它是一个。net的HTTP客户端库，具有一个流畅的接口，特别支持使用它来发出HTTP请求的代码的可测试性。
网站上有很多代码示例，但简单地说，你在代码中是这样使用的。
添加用途。
using Flurl;
using Flurl.Http;
发送get请求并读取响应。
public async Task SendGetRequest()
{
var response = await "https://example.com".GetAsync();
// ...
}
在单元测试中，Flurl充当一个模拟，可以将其配置为所需的行为，还可以验证所执行的调用。
using (var httpTest = new HttpTest())
{
// Arrange
httpTest.RespondWith("OK", 200);
// Act
await sut.SendGetRequest();
// Assert
httpTest.ShouldHaveCalled("https://example.com")
.WithVerb(HttpMethod.Get);
}
我同意其他一些回答，最好的方法是在HttpClient内部模拟HttpMessageHandler，而不是包装HttpClient。这个答案是唯一的，因为它仍然注入HttpClient，允许它成为一个单例或者使用依赖注入进行管理。
HttpClient打算被实例化一次，并在整个过程中被重用
应用程序的生命周期。
(来源)。
模拟HttpMessageHandler可能有点棘手，因为SendAsync是受保护的。下面是一个使用xunit和Moq的完整示例。
using System;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using Moq;
using Moq.Protected;
using Xunit;
// Use nuget to install xunit and Moq
namespace MockHttpClient {
class Program {
static void Main(string[] args) {
var analyzer = new SiteAnalyzer(Client);
var size = analyzer.GetContentSize("http://microsoft.com").Result;
Console.WriteLine($"Size: {size}");
}
private static readonly HttpClient Client = new HttpClient(); // Singleton
}
public class SiteAnalyzer {
public SiteAnalyzer(HttpClient httpClient) {
_httpClient = httpClient;
}
public async Task<int> GetContentSize(string uri)
{
var response = await _httpClient.GetAsync( uri );
var content = await response.Content.ReadAsStringAsync();
return content.Length;
}
private readonly HttpClient _httpClient;
}
public class SiteAnalyzerTests {
[Fact]
public async void GetContentSizeReturnsCorrectLength() {
// Arrange
const string testContent = "test content";
var mockMessageHandler = new Mock<HttpMessageHandler>();
mockMessageHandler.Protected()
.Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
.ReturnsAsync(new HttpResponseMessage {
StatusCode = HttpStatusCode.OK,
Content = new StringContent(testContent)
});
var underTest = new SiteAnalyzer(new HttpClient(mockMessageHandler.Object));
// Act
var result = await underTest.GetContentSize("http://anyurl");
// Assert
Assert.Equal(testContent.Length, result);
}
}
}
