在单元测试HttpClient时如何模拟GetDiscoveryDocumentAsync？

Question

我正在尝试为HttpClient服务编写一些单元测试，并且在尝试模拟GetAccessToken（）函数中的部分代码时遇到问题。

该服务接受一个I​​HttpClientFactory。从到目前为止的阅读看来，要正确地模拟它，我必须模拟IHttpClientFactory，让它返回依赖于模拟的HttpMessageHandler的新HttpClient，我这样做是这样的：

var mockHttpClientFactory = new Mock<IHttpClientFactory>();

var mockHttpMessageHandler = new Mock<HttpMessageHandler>();
mockHttpMessageHandler.Protected()
    .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
    .ReturnsAsync(new HttpResponseMessage
        {
         StatusCode = HttpStatusCode.OK,
         Content = new StringContent("{'name':thecodebuzz,'city':'USA'}"),
        });

var client = new HttpClient(mockHttpMessageHandler.Object);
mockHttpClientFactory.Setup(x => x.CreateClient(It.IsAny<string>())).Returns(client);

_httpClientService = new HttpClientService(mockHttpClientFactory.Object, mockConfig.Object); 

此方面有效，我已经能够调用运行正常的CreateClient（）了。但是，我要测试的函数调用了我的GetAccessToken（）函数，该函数又调用了client.GetDiscoveryAccessToken（）。我猜想GetDiscoveryAccessToken（）函数需要被模拟，但是我不确定如何继续。

我尝试用模拟方法创建客户端模拟，并在像这样调用CreateClient时返回此模拟：

 var discoDoc = // Mocked disco doc code;

 var client = new Mock<HttpClient>(mockHttpMessageHandler.Object);
 client.Setup(x => x.GetDiscoveryDocumentAsync(It.IsAny<string>())).Returns(discoDoc);

 mockHttpClientFactory.Setup(x => x.CreateClient(It.IsAny<string>())).Returns(client);

 _httpClientService = new HttpClientService(mockHttpClientFactory.Object, mockConfig.Object);

[不幸的是，我收到此错误：“无法从'Moq.Mock'转换为'System.Net.Http.HttpClient'”，我告诉CreateClient函数返回什么。我猜这是因为我需要返回一个真正的HttpClient而不是模拟的。

关于我可以从这里去哪里的任何想法？

Answer 1

您几乎在那里，对于CreateClient，您将返回Moq的对象，而不是模拟的对象。只需返回如下所示的模拟对象即可。

 var discoDoc = // Mocked disco doc code;

 var client = new Mock<HttpClient>(mockHttpMessageHandler.Object);
 client.Setup(x => x.GetDiscoveryDocumentAsync(It.IsAny<string>())).Returns(discoDoc);

 mockHttpClientFactory.Setup(x => x.CreateClient(It.IsAny<string>())).Returns(client.Object);

 _httpClientService = new HttpClientService(mockHttpClientFactory.Object, mockConfig.Object);

让我知道这是否是您所期望的。