ASP.NET Core单元测试中如何Mock HttpClient.GetStringAsync()的示例分析

ASP.NET Core单元测试中如何Mock HttpClient.GetStringAsync()的示例分析，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。

在 ASP.NET Core 单元测试中模拟HttpClient.GetStringAsync() 的技巧。

问题

下面这个代码

var html = await _httpClient.GetStringAsync(sourceUrl);

如果按正常思路像这样去 Mock HttpClient.GetStringAsync()

var httpClientMock = new Mock(); httpClientMock     .Setup(p => p.GetStringAsync(It.IsAny()))     .Returns(Task.FromResult("..."));

Moq 框架就会爆

Exception

System.NotSupportedException : Unsupported expression: p => p.GetStringAsync(It.IsAny())Non-overridable members (here: HttpClient.GetStringAsync) may not be used in setup / verification expressions.

解决方法

我们需要 Mock HttpClient 底层使用的 HttpMessageHandler 而不是 HttpClient

var handlerMock = new Mock(); var magicHttpClient = new HttpClient(handlerMock.Object);

然后我花了 9.96 分钟研究了 HttpClient.GetStringAsync() 的源代码，发现它最终调用的是 SendAsync() 方法

private async Task GetStringAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken) {     // ...     response = await base.SendAsync(request, cts.Token).ConfigureAwait(false);     // ... }

源代码位置：https://source.dot.net/#System.Net.Http/System/Net/Http/HttpClient.cs,170

因此，我们的 Mock Setup 如下：

handlerMock     .Protected()     .Setup>(         "SendAsync",         ItExpr.IsAny(),         ItExpr.IsAny()     )     .ReturnsAsync(new HttpResponseMessage     {         StatusCode = HttpStatusCode.OK,         Content = new StringContent("the string you want to return")     })     .Verifiable();

现在 Mock 就能运行成功了!

最后附上完整的 UT 代码供参考：

using System.Net; using System.Net.Http; using System.Threading; using System.Threading.Tasks; using Microsoft.Extensions.Logging; using Moq; using Moq.Protected; using NUnit.Framework;  namespace Moonglade.Pingback.Tests {     [TestFixture]     public class PingSourceInspectorTests     {         private MockRepository _mockRepository;          private Mock> _mockLogger;         private Mock _handlerMock;         private HttpClient _magicHttpClient;          [SetUp]         public void SetUp()         {             _mockRepository = new(MockBehavior.Default);             _mockLogger = _mockRepository.Create>();             _handlerMock = _mockRepository.Create();         }          private PingSourceInspector CreatePingSourceInspector()         {             _magicHttpClient = new(_handlerMock.Object);             return new(_mockLogger.Object, _magicHttpClient);         }          [Test]         public async Task ExamineSourceAsync_StateUnderTest_ExpectedBehavior()         {             string sourceUrl = "https://996.icu/work-996-sick-icu";             string targetUrl = "https://greenhat.today/programmers-special-gift";              _handlerMock                 .Protected()                 .Setup>(                     "SendAsync",                     ItExpr.IsAny(),                     ItExpr.IsAny()                 )                 .ReturnsAsync(new HttpResponseMessage                 {                     StatusCode = HttpStatusCode.OK,                     Content = new StringContent($"" +                                                 $"" +                                                 $"" +                                                 $"" +                                                 $"Work 996 and have a green hat!" +                                                 $"")                 })                 .Verifiable();             var pingSourceInspector = CreatePingSourceInspector();              var result = await pingSourceInspector.ExamineSourceAsync(sourceUrl, targetUrl);             Assert.IsFalse(result.ContainsHtml);             Assert.IsTrue(result.SourceHasLink);             Assert.AreEqual("Programmer's Gift", result.Title);             Assert.AreEqual(targetUrl, result.TargetUrl);             Assert.AreEqual(sourceUrl, result.SourceUrl);         }     } }

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