使用Moq测试Polly重试策略

Question

我正在尝试为 Polly 写单元测试，但似乎返回值已被缓存。

方法 PostAsyncWithRetry:

using Polly;
using System;
using System.Diagnostics;
using System.Net.Cache;
using System.Net.Http;
public class RetryClient
{
    private HttpClient httpClient = new HttpClient(new WebRequestHandler()
    { CachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore) });

    public HttpResponseMessage PostAsyncWithRetry(
        String url,
        String path,
        StringContent httpContent)
    {
        httpClient.BaseAddress = new Uri(url);

        var retryPolicy =
            Policy.Handle<HttpRequestException>()
            .OrResult<HttpResponseMessage>(r => !r.IsSuccessStatusCode)
            .RetryAsync(3, (exception, retryCount, context) =>
            {
                Debug.WriteLine("RetryCount: {0}", retryCount);
            });

        var response = retryPolicy.ExecuteAsync(async () =>
        {
            return await httpClient.PostAsync(path, httpContent);
        }
        );

        return response.Result;
    }
}

测试：

[TestFixture]
class Test
{
    private HttpClient mockHTTPClient;
    private Mock<WebRequestHandler> mockHttpMessageHandler;
    private RetryClient testInstance;

    private const String URL = "https://aaa.com";
    private const String PATH = "/path";
    private const String EXPECTED_STRING_CONTENT = "Some return text";

    [SetUp]
    public void SetUp()
    {
        testInstance = new RetryClient();
        mockHttpMessageHandler = new Mock<WebRequestHandler>();
        mockHttpMessageHandler.Object.CachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore);

        mockHTTPClient = new HttpClient(mockHttpMessageHandler.Object);

        var type = typeof(RetryClient);
        var fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance);
        fields[0].SetValue(testInstance, mockHTTPClient);
    }

    [Test]
    public void TestMEEEE()
    {
        var responses = new Queue<Task<HttpResponseMessage>>();
        responses.Enqueue(Task.FromResult(new HttpResponseMessage
        {
            StatusCode = HttpStatusCode.NotFound,
            Content = new StringContent(EXPECTED_STRING_CONTENT)
        }));
        responses.Enqueue(Task.FromResult(new HttpResponseMessage
        {
            StatusCode = HttpStatusCode.OK,
            Content = new StringContent(EXPECTED_STRING_CONTENT)
        }));

        var postContent = new StringContent(EXPECTED_STRING_CONTENT);
        mockHttpMessageHandler.Protected()
           .Setup<Task>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
           .Returns(responses.Dequeue());

        var response = testInstance.PostAsyncWithRetry(
            URL, PATH, postContent);

        mockHttpMessageHandler.Verify();
        Assert.AreEqual(responses.Count, 0, "didn't dequeue");
        Assert.AreEqual(HttpStatusCode.OK, response.StatusCode, "Incorrect status code");
    }

}

不确定为什么，但似乎响应队列只被出队一次，这让我相信响应正在被缓存。有人知道是谁在缓存响应，以及如何禁用它吗？

提前感谢您的帮助！

- Karis

---

请尽可能提供真实的 [mcve]，因为不清楚这两个片段如何交互。 旁注：使用 .Result 会使方法非异步，并可能发生死锁，但在单元测试中不太可能出现问题。 - Alexei Levenkov

这里有一些你可以看看的：https://github.com/App-vNext/Polly/blob/master/src/Polly.SharedSpecs/Retry/RetrySpecs.cs - Scott Hannen

@ScottHannen分享了RetrySpec.cs的当前URL。 - spottedmahn

Answer 1

我想通了，这与缓存无关。在模拟设置期间，它将Dequeue值存储为返回值，而不是每次调用它。 现在将其更改为() => responses.Dequeue()即可解决。

谢谢大家！

- Karis

---

谢谢你的提问和回答。今天它对我帮助很大。 - upsidedownwf