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?
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。
这里有一个简单的解决方法，对我来说很有效。
使用moq mock库。
// ARRANGE
var handlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);
handlerMock
.Protected()
// Setup the PROTECTED method to mock
.Setup<Task<HttpResponseMessage>>(
"SendAsync",
ItExpr.IsAny<HttpRequestMessage>(),
ItExpr.IsAny<CancellationToken>()
)
// prepare the expected response of the mocked http call
.ReturnsAsync(new HttpResponseMessage()
{
StatusCode = HttpStatusCode.OK,
Content = new StringContent("[{'id':1,'value':'1'}]"),
})
.Verifiable();
// use real http client with mocked handler here
var httpClient = new HttpClient(handlerMock.Object)
{
BaseAddress = new Uri("http://test.com/"),
};
var subjectUnderTest = new MyTestClass(httpClient);
// ACT
var result = await subjectUnderTest
.GetSomethingRemoteAsync('api/test/whatever');
// ASSERT
result.Should().NotBeNull(); // this is fluent assertions here...
result.Id.Should().Be(1);
// also check the 'http' call was like we expected it
var expectedUri = new Uri("http://test.com/api/test/whatever");
handlerMock.Protected().Verify(
"SendAsync",
Times.Exactly(1), // we expected a single external request
ItExpr.Is<HttpRequestMessage>(req =>
req.Method == HttpMethod.Get // we expected a GET request
&& req.RequestUri == expectedUri // to this uri
),
ItExpr.IsAny<CancellationToken>()
);
来源:https://gingter.org/2018/07/26/how-to-mock-httpclient-in-your-net-c-unit-tests/
正如注释中提到的，您需要抽象HttpClient，这样就不会与它耦合。我以前也做过类似的事情。我会试着把我的方法和你们要做的方法相适应。
首先看一下HttpClient类，并决定需要它提供哪些功能。
以下是一种可能性:
public interface IHttpClient {
System.Threading.Tasks.Task<T> DeleteAsync<T>(string uri) where T : class;
System.Threading.Tasks.Task<T> DeleteAsync<T>(Uri uri) where T : class;
System.Threading.Tasks.Task<T> GetAsync<T>(string uri) where T : class;
System.Threading.Tasks.Task<T> GetAsync<T>(Uri uri) where T : class;
System.Threading.Tasks.Task<T> PostAsync<T>(string uri, object package);
System.Threading.Tasks.Task<T> PostAsync<T>(Uri uri, object package);
System.Threading.Tasks.Task<T> PutAsync<T>(string uri, object package);
System.Threading.Tasks.Task<T> PutAsync<T>(Uri uri, object package);
}
如前所述，这是为了特定目的。我完全抽象出了对HttpClient的依赖，并专注于我想要返回的东西。您应该评估如何抽象HttpClient以只提供您想要的必要功能。
这将允许您只模拟需要测试的内容。
我甚至建议完全放弃IHttpHandler，而使用HttpClient抽象IHttpClient。但我只是没有选择，因为你可以用抽象客户端的成员替换你的处理程序接口的主体。
IHttpClient的实现可以用来包装/改编一个真正的/具体的HttpClient或任何其他对象，它可以用来发出HTTP请求，因为你真正想要的是一个服务，它提供了与HttpClient相反的功能。使用抽象是一种干净(我的观点)和可靠的方法，并且可以使您的代码更易于维护，如果您需要在框架更改时将底层客户端切换为其他东西。
下面是如何实现的代码片段。
/// <summary>
/// HTTP Client adaptor wraps a <see cref="System.Net.Http.HttpClient"/>
/// that contains a reference to <see cref="ConfigurableMessageHandler"/>
/// </summary>
public sealed class HttpClientAdaptor : IHttpClient {
HttpClient httpClient;
public HttpClientAdaptor(IHttpClientFactory httpClientFactory) {
httpClient = httpClientFactory.CreateHttpClient(**Custom configurations**);
}
//...other code
/// <summary>
/// Send a GET request to the specified Uri as an asynchronous operation.
/// </summary>
/// <typeparam name="T">Response type</typeparam>
/// <param name="uri">The Uri the request is sent to</param>
/// <returns></returns>
public async System.Threading.Tasks.Task<T> GetAsync<T>(Uri uri) where T : class {
var result = default(T);
//Try to get content as T
try {
//send request and get the response
var response = await httpClient.GetAsync(uri).ConfigureAwait(false);
//if there is content in response to deserialize
if (response.Content.Headers.ContentLength.GetValueOrDefault() > 0) {
//get the content
string responseBodyAsText = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
//desrialize it
result = deserializeJsonToObject<T>(responseBodyAsText);
}
} catch (Exception ex) {
Log.Error(ex);
}
return result;
}
//...other code
}
正如你在上面的例子中所看到的，很多通常与使用HttpClient相关的繁重工作都隐藏在抽象后面。
然后可以用抽象客户端注入连接类
public class Connection
{
private IHttpClient _httpClient;
public Connection(IHttpClient httpClient)
{
_httpClient = httpClient;
}
}
然后，您的测试可以模拟SUT所需的内容
private IHttpClient _httpClient;
[TestMethod]
public void TestMockConnection()
{
SomeModelObject model = new SomeModelObject();
var httpClientMock = new Mock<IHttpClient>();
httpClientMock.Setup(c => c.GetAsync<SomeModelObject>(It.IsAny<string>()))
.Returns(() => Task.FromResult(model));
_httpClient = httpClientMock.Object;
var client = new Connection(_httpClient);
// Assuming doSomething uses the client to make
// a request for a model of type SomeModelObject
client.doSomething();
}
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);
}
}
}
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。
