使用 moq 模拟 HttpMessageHandler - 如何获取请求的内容？

问题描述

在决定我想为测试发回什么样的响应之前，有没有办法获取http请求的内容？多个测试将使用此类，每个测试将有多个 http 请求。此代码无法编译，因为 lambda 不是异步的，并且其中有一个等待。我是 async-await 的新手，所以我不确定如何解决这个问题。我曾短暂考虑过拥有多个 TestHttpClientFactories，但这意味着代码重复，因此如果可能，我决定反对它。任何帮助表示赞赏。

public class TestHttpClientFactory : IHttpClientFactory
{
    public HttpClient CreateClient(string name)
    {
        var messageHandlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);

        messageHandlerMock.Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync",ItExpr.IsAny<HttpRequestMessage>(),ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync((HttpRequestMessage request,CancellationToken token) =>
            {
                HttpResponseMessage response = new HttpResponseMessage();
                var requestMessageContent = await request.Content.ReadAsstringAsync();

                // decide what to put in the response after looking at the contents of the request

                return response;
            })
            .Verifiable();

        var httpClient = new HttpClient(messageHandlerMock.Object);
        return httpClient;
    }
}

解决方法

要利用异步委托，请改用 Returns 方法

public class TestHttpClientFactory : IHttpClientFactory {
    public HttpClient CreateClient(string name) {
        var messageHandlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);

        messageHandlerMock.Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync",ItExpr.IsAny<HttpRequestMessage>(),ItExpr.IsAny<CancellationToken>())
            .Returns(async (HttpRequestMessage request,CancellationToken token) => {
                
                string requestMessageContent = await request.Content.ReadAsStringAsync();

                HttpResponseMessage response = new HttpResponseMessage();

                //...decide what to put in the response after looking at the contents of the request

                return response;
            })
            .Verifiable();

        var httpClient = new HttpClient(messageHandlerMock.Object);
        return httpClient;
    }
}

或者考虑创建您自己的处理程序，公开一个委托来处理所需的行为。

例如

public class DelegatingHandlerStub : DelegatingHandler {
    private readonly Func<HttpRequestMessage,CancellationToken,Task<HttpResponseMessage>> _handlerFunc;
    public DelegatingHandlerStub() {
        _handlerFunc = (request,cancellationToken) => Task.FromResult(request.CreateResponse(HttpStatusCode.OK));
    }

    public DelegatingHandlerStub(Func<HttpRequestMessage,Task<HttpResponseMessage>> handlerFunc) {
        _handlerFunc = handlerFunc;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,CancellationToken cancellationToken) {
        return _handlerFunc(request,cancellationToken);
    }
}

并在工厂中像这样使用

public class TestHttpClientFactory : IHttpClientFactory {
    public HttpClient CreateClient(string name) {
        var messageHandlerMock = new DelegatingHandlerStub(async (HttpRequestMessage request,CancellationToken token) => {
                
            string requestMessageContent = await request.Content.ReadAsStringAsync();

            HttpResponseMessage response = new HttpResponseMessage();

            //...decide what to put in the response after looking at the contents of the request

            return response;
        });

        var httpClient = new HttpClient(messageHandlerMock);
        return httpClient;
    }
}