模拟HttpClient SendAsync方法

Question

我的代码使用HttpClient来检索一些数据

HttpClient client = new HttpClient
{
    BaseAddress = new Uri("myurl.com"),
};
var msg = new HttpRequestMessage(HttpMethod.Get, "myendpoint");
var res = await client.SendAsync(msg);

我如何在HttpClient上模拟这个HttpClient方法并将其注入.net核心ServiceCollection中？

我试着像这样嘲弄

var mockFactory = 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);
            mockFactory.Setup(_ => _.CreateClient(It.IsAny<string>())).Returns(client);

但是如何将这个mockFactory注入ServiceCollection呢？或者也许有更简单的或不同的方法？

Answer 1

为什么不对HTTP调用进行封装，而不是模拟它呢？然后您可以模拟封装/抽象。

例如：

interface IClient
{
  Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken = default);
}

class HttpClientAdapter : IClient
{
  readonly HttpClient _client;

  public HttpClientAdapter(HttpClient client)
  {
    _client = client;
  }

  public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken = default) => _client.SendAsync(request, cancellationToken);
}

使您的代码依赖于IClient接口。在正常使用期间，您将在HttpClient实现中使用真正的HttpClientAdapter。对于测试，您可以模拟IClient。

注意，将抽象级别提高一点对您可能更有用。例如，如果您希望将来自HTTP响应的JSON字符串解析为某些DataObject，那么您的IClient接口应该更像这样：

class DataObject
{
  public string Name { get; set; }
  public string City { get; set; }
}

interface IClient
{
  Task<DataObject> GetAsync(CancellationToken cancellationToken = default);
}

public class ClientImplementation : IClient
{
  readonly HttpClient _client;

  public ClientImplementation(HttpClient client)
  {
    _client = client;
  }

  public async Task<DataObject> GetAsync(CancellationToken cancellationToken = default)
  {
    var response = await _client.SendAsync(...);
    var dataObject = new DataObject();
    // parse the response into the data object
    return dataObject;
  }
}

在这里划定界限的好处是您的测试将有较少的工作要做。例如，您的模拟代码不必设置HttpResponseMessage对象。

你选择在哪里为你的抽象划定界限完全取决于你自己。但关键是:一旦代码依赖于一个小接口，那么就很容易模拟该接口并测试您的代码。

Answer 2

如果您真的需要模拟HttpClient本身，请看下面的lib：https://github.com/richardszalay/mockhttp

从医生那里：

var mockHttp = new MockHttpMessageHandler();

// Setup a respond for the user api (including a wildcard in the URL)
mockHttp.When("http://localhost/api/user/*")
        .Respond("application/json", "{'name' : 'Test McGee'}"); // Respond with JSON

// Inject the handler or client into your application code
var client = mockHttp.ToHttpClient();

var response = await client.GetAsync("http://localhost/api/user/1234");
// or without async: var response = client.GetAsync("http://localhost/api/user/1234").Result;

var json = await response.Content.ReadAsStringAsync();

// No network connection required
Console.Write(json); // {'name' : 'Test McGee'}