c# - 如何使用 Moq 在 .NET Core 2.1 中模拟新的 HttpClientFactory

Question

.NET Core 2.1 附带了这个名为 HttpClientFactory 的新工厂，但我无法弄清楚如何模拟它以对包含 REST 服务调用的某些方法进行单元测试。

正在使用 .NET Core IoC 容器注入(inject)工厂，该方法所做的是从工厂创建一个新的客户端:

var client = _httpClientFactory.CreateClient();

然后使用客户端从 REST 服务获取数据:

var result = await client.GetStringAsync(url);

Answer 1

HttpClientFactory 派生自 IHttpClientFactory Interface所以这只是创建一个模拟界面的问题

var mockFactory = new Mock<IHttpClientFactory>();

根据您需要客户端的用途，您需要设置模拟以返回用于测试的 HttpClient。

然而，这需要一个实际的 HttpClient。

var clientHandlerStub = new DelegatingHandlerStub();
var client = new HttpClient(clientHandlerStub);

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

IHttpClientFactory factory = mockFactory.Object;

然后可以在进行测试时将工厂注入(inject)到被测依赖系统中。

如果您不希望客户端调用实际的端点，那么您将需要创建一个假的委托(delegate)处理程序来拦截请求。

用于伪造请求的处理程序 stub 示例

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, CancellationToken, Task<HttpResponseMessage>> handlerFunc) {
        _handlerFunc = handlerFunc;
    }

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

摘 self 在这里给出的答案

引用 Mock HttpClient using Moq

假设你有一个 Controller

[Route("api/[controller]")]
public class ValuesController : Controller {
    private readonly IHttpClientFactory _httpClientFactory;

    public ValuesController(IHttpClientFactory httpClientFactory) {
        _httpClientFactory = httpClientFactory;
    }

    [HttpGet]
    public async Task<IActionResult> Get() {
        var client = _httpClientFactory.CreateClient();
        var url = "http://example.com";
        var result = await client.GetStringAsync(url);
        return Ok(result);
    }
}

并想测试 Get() 操作。

public async Task Should_Return_Ok() {
    //Arrange
    var expected = "Hello World";
    var mockFactory = new Mock<IHttpClientFactory>();
    var configuration = new HttpConfiguration();
    var clientHandlerStub = new DelegatingHandlerStub((request, cancellationToken) => {
        request.SetConfiguration(configuration);
        var response = request.CreateResponse(HttpStatusCode.OK, expected);
        return Task.FromResult(response);
    });
    var client = new HttpClient(clientHandlerStub);
    
    mockFactory.Setup(_ => _.CreateClient(It.IsAny<string>())).Returns(client);
    
    IHttpClientFactory factory = mockFactory.Object;
    
    var controller = new ValuesController(factory);
    
    //Act
    var result = await controller.Get();
    
    //Assert
    result.Should().NotBeNull();
    
    var okResult = result as OkObjectResult;
    
    var actual = (string) okResult.Value;
    
    actual.Should().Be(expected);
}