在 ConfigureServices 中使用自定义 HttpClient 和 Polly 策略对核心 API 控制器进

Question

我在使用Polly和HttpClient时执行单元测试时遇到问题。

具体来说，Polly 和 HttpClient 用于 ASP.NET 核心 Web API 控制器，链接如下：

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-requests

https://github.com/App-vNext/Polly/wiki/Polly-and-HttpClientFactory

问题(1 和 2)在底部指定。我想知道这是否是使用Polly和HttpClient的正确方法.

配置服务

配置 Polly 策略并单独自定义 HttpClient，CustomHttpClient

public void ConfigureServices(IServiceCollection services)
{
services.AddHttpClient();
services.AddHttpClient<HttpClientService>()                                
.AddPolicyHandler((service, request) =>
HttpPolicyExtensions.HandleTransientHttpError()
.WaitAndRetryAsync(3,
retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))
);
}

汽车控制器

CarController 依赖于HttpClientService，它是由框架自动注入的，无需显式注册。

请注意，HttpClientService会导致单元测试出现问题，因为Moq无法模拟非虚拟方法，稍后会提到。

[ApiVersion("1")]
[Route("api/v{version:apiVersion}/[controller]")]
[ApiController]
public class CarController : ControllerBase
{
private readonly ILog _logger;
private readonly HttpClientService _httpClientService;
private readonly IOptions<Config> _config;
public CarController(ILog logger, HttpClientService httpClientService, IOptions<Config> config)
{
_logger = logger;
_httpClientService = httpClientService;
_config = config;
}
[HttpPost]
public async Task<ActionResult> Post()
{  
using (StreamReader reader = new StreamReader(Request.Body, Encoding.UTF8))
{
string body = reader.ReadToEnd();
var statusCode = await _httpClientService.PostAsync(
"url",
new Dictionary<string, string>
{
{"headerID", "Id"}                           
},
body);
return StatusCode((int)statusCode);               
}
}
}

HttpClientService

Simiar toCarController，HttpClientService有一个单元测试的问题，因为HttpClient的后期异步不能被模拟。 框架会自动注入HttpClient，无需显式注册。

public class HttpClientService
{
private readonly HttpClient _client;
public HttpClientService(HttpClient client)
{
_client = client;
}
public async Task<HttpStatusCode> PostAsync(string url, Dictionary<string, string> headers, string body)
{
using (var content = new StringContent(body, Encoding.UTF8, "application/json"))
{
foreach (var keyValue in headers)
{
content.Headers.Add(keyValue.Key, keyValue.Value);
}
var response = await _client.PostAsync(url, content);
response.EnsureSuccessStatusCode();
return response.StatusCode;
}
}

问题1

单元测试：Moq不能模拟HttpClientService的PostAsync方法。我可以将其更改为虚拟，但我想知道它是否是最佳选择。

public class CarControllerTests
{
private readonly Mock<ILog> _logMock;
private readonly Mock<HttpClient> _httpClientMock;
private readonly Mock<HttpClientService> _httpClientServiceMock;
private readonly Mock<IOptions<Config>> _optionMock;
private readonly CarController _sut;

public CarControllerTests()  //runs for each test method
{
_logMock = new Mock<ILog>();
_httpClientMock = new Mock<HttpClient>();
_httpClientServiceMock = new Mock<HttpClientService>(_httpClientMock.Object);
_optionMock = new Mock<IOptions<Config>>();
_sut = new CarController(_logMock.Object, _httpClientServiceMock.Object, _optionMock.Object);
}
[Fact]
public void Post_Returns200()
{
//System.NotSupportedException : Invalid setup on a non-virtual (overridable in VB) member
_httpClientServiceMock.Setup(hc => hc.PostAsync(It.IsAny<string>(),
It.IsAny<Dictionary<string, string>>(),
It.IsAny<string>()))
.Returns(Task.FromResult(HttpStatusCode.OK));
}
}

}

问题2

单元测试：与HttpClientService类似，Moq不能模拟HttpClient的PostAsync方法。

public class HttpClientServiceTests
{
[Fact]
public void Post_Returns200()
{
var httpClientMock = new Mock<HttpClient>();
//System.NotSupportedException : Invalid setup on a non-virtual (overridable in VB) member
httpClientMock.Setup(hc => hc.PostAsync("", It.IsAny<HttpContent>()))
.Returns(Task.FromResult(new HttpResponseMessage()));
}
}

ASP.NET 核心接口 2.2

更新

更正了 CustomHttpClient 到 HttpClientService 的拼写错误

更新 2

问题 2 的解决方案

Answer 1

假设CustomHttpClient是一个错别字，HttpClientService是实际的依赖关系，控制器与实现问题紧密耦合，正如您已经经历的那样，很难单独测试(单元测试)。

将这些凝固物封装在抽象之后

public interface IHttpClientService {
Task<HttpStatusCode> PostAsync(string url, Dictionary<string, string> headers, string body);
}

public class HttpClientService : IHttpClientService {
//...omitted for brevity
}

可以在测试时替换。

重构控制器以依赖于抽象而不是具体实现

public class CarController : ControllerBase {
private readonly ILog _logger;
private readonly IHttpClientService httpClientService; //<-- TAKE NOTE
private readonly IOptions<Config> _config;
public CarController(ILog logger, IHttpClientService httpClientService, IOptions<Config> config) {
_logger = logger;
this.httpClientService = httpClientService;
_config = config;
}
//...omitted for brevity
}

更新服务配置以使用允许注册抽象及其实现的重载

public void ConfigureServices(IServiceCollection services) {
services.AddHttpClient();
services
.AddHttpClient<IHttpClientService, HttpClientService>() //<-- TAKE NOTE
.AddPolicyHandler((service, request) =>
HttpPolicyExtensions.HandleTransientHttpError()
.WaitAndRetryAsync(3,
retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))
);
}

这负责重新调整代码以使其对测试更友好。

下面显示了现在可以单独对控制器进行单元测试

public class CarControllerTests {
private readonly Mock<ILog> _logMock;
private readonly Mock<IHttpClientService> _httpClientServiceMock;
private readonly Mock<IOptions<Config>> _optionMock;
private readonly CarController _sut;

public CarControllerTests()  //runs for each test method 
{
_logMock = new Mock<ILog>();
_httpClientServiceMock = new Mock<IHttpClientService>();
_optionMock = new Mock<IOptions<Config>>();
_sut = new CarController(_logMock.Object, _httpClientServiceMock.Object, _optionMock.Object);
}
[Fact]
public async Task Post_Returns200() {
//Arrange
_httpClientServiceMock
.Setup(_ => _.PostAsync(
It.IsAny<string>(),
It.IsAny<Dictionary<string, string>>(),
It.IsAny<string>())
)
.ReturnsAsync(HttpStatusCode.OK);
//Act
//...omitted for brevity
//...
}
}

请注意，不再需要完成测试的HttpClient。

控制器还需要确保安排其他依赖项才能使测试流动，但这目前不在问题的范围之内。