XUnit模擬方法，但不返回預期結果

Question

我在XUnit測試中使用了Moq，但由於某種原因，該模擬無法正常工作。 這是我的單元測試：

 [Fact]
        public async Task SampleUnitTest()
        {
            //Arrange
            var httpClient = new HttpClient(new FakeHttpMessageHandler());
            _mockConstructRequest.Setup(x => x.ConstructRequestString(searchRequestModel))
                                 .Returns("a sample string");
            var service = new LibraryService(_mockConstructRequest.Object);

            //Act
            var response = service.GetResponse(new Request(), httpClient);

            //Assert
            response.Should().BeNull();

        }

         private class FakeHttpMessageHandler : HttpMessageHandler
        {
            public Func<HttpRequestMessage, CancellationToken, HttpResponseMessage> HttpRequestHandler { get; set; } =
            (r, c) =>
                new HttpResponseMessage
                {
                    ReasonPhrase = r.RequestUri.AbsoluteUri,
                    StatusCode = HttpStatusCode.OK
                };


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

這是實際的代碼，我正在嘗試測試GetResponse方法。

  public class LibraryService : ILibraryService
 {
    private IConfiguration _configuration;
    private IRequestConstructor _requestContructor;
    public LibraryService (IRequestConstructor requestConstructor)
    {
        _requestConstructor = requestConstructor;
    }

    public async Task<Response> GetResponse(Request request, HttpClient client)
        {

            //construct request
            string requestString = _constructRequestString.ConstructRequestString(request, client);

            return null;
        }
 }

 public class RequestContructor : IRequestContructor
 {
  public string ConstructRequestString(Request request)
        {
            return "a request string";
        }
 }

我試圖從單元測試中逐步檢查代碼，但是當斷點在這一行時， requestString變量為null，而它應該返回“樣本字符串”。 有人知道為什么嗎？

string requestString = _constructRequestString.ConstructRequestString(request, client);

Answer 1

據我所知，您的模擬是錯誤的：模擬：

_mockConstructRequest.Setup(x => x.ConstructRequestString(searchRequestModel))
                                 .Returns("a sample string");

您正在調用的方法：

_constructRequestString.ConstructRequestString(request, client);

不應該是這樣的：

_mockConstructRequest.Setup(x => x.ConstructRequestString(It.IsAny<Request>(),It.IsAny<HttpClient>()))
                                 .Returns("a sample string");

最重要的是：

嘗試在構造函數中而不是在每個測試中初始化模擬和“ classUnderTest”，它將在測試之前每次運行，並為您做所有事情。 例如：

public class UnitTestClass{

private readonly ClassUnderTest _classUnderTest;
private readonly Mock<ClassUnderTestDependecy> mockedInstance;

public UnitTestClass {
mockedInstance= new Mock<ClassUnderTestDependecy>();
_classUnderTest= new ClassUnderTest (ClassUnderTestDependecy.Object);
}

}