C# 模拟 IHttpclient & CreateClient

Question

我有一个函数想要进行 x 单元测试，但似乎我必须模拟 CreateClient 函数？每当我在测试期间调试它时，var client 似乎等于 null。我确信我正在正确注入依赖项。我想知道的是如何模拟 CreateClient。

这是该函数：

    public async Task CreateMessageHistoryAsync(Message message)
    {
        //This seems to be giving a null value
        var client = this.clientFactory.CreateClient(NamedHttpClients.COUCHDB);

        var formatter = new JsonMediaTypeFormatter();
        formatter.SerializerSettings = new JsonSerializerSettings
        {
            Formatting = Formatting.Indented,
            NullValueHandling = NullValueHandling.Ignore,
            ContractResolver = new CamelCasePropertyNamesContractResolver()
        };

        Guid id = Guid.NewGuid();            

        var response = await client.PutAsync(id.ToString(), message, formatter);

        if (!response.IsSuccessStatusCode)
        {
            throw new HttpRequestException(await response.Content.ReadAsStringAsync());
        }
    }

这是单元测试，我在一个单独的类中模拟 IHttpClient 并且我正在使用该类。

    [Collection("MockStateCollection")]
    public class CreateMessageHistory
    {
        private readonly MockStateFixture mockStateFixture;

        public CreateMessageHistory(MockStateFixture mockStateFixture)
        {
            this.mockStateFixture = mockStateFixture;
        }

        [Fact]
        public async Task Should_NotThrowHttpRequestException_When_AMessageHistoryIsCreated()
        {
            var recipients = MockMessage.GetRecipients("Acc", "Site 1", "Site 2", "Site 3");
            var message = MockMessage.GetMessage(recipients);

            mockStateFixture
                .MockMessageHistoryService
                .Setup(service => service.CreateMessageHistoryAsync(message));

            var messageHistoryService = new MessageHistoryService(
                mockStateFixture.MockIHttpClientFactory.Object);

            mockStateFixture.MockIHttpClientFactory.Object.CreateClient("CouchDB");

            var task = messageHistoryService.CreateMessageHistoryAsync(message);
            var type = task.GetType();
            Assert.True(type.GetGenericArguments()[0].Name == "VoidTaskResult");
            Assert.True(type.BaseType == typeof(Task));
            await task;

            //await Assert.IsType<Task>(messageHistoryService.CreateMessageHistoryAsync(message));
            // await Assert.ThrowsAsync<HttpRequestException>(() => messageHistoryService.CreateMessageHistoryAsync(message));
        }
    }

在我看来，我还需要模拟 CreateClient 类，是吗？

Answer 1

您应该为已设置

ClientFactory

方法的

CreateClient

注入一个模拟对象。

// create the mock client
var httpClient = new Mock<IHttpClient>();

// setup method call for client
httpClient.Setup(x=>x.PutAsync(It.IsAny<string>()
                               , It.IsAny<Message>(),
                               , It.IsAny< JsonMediaTypeFormatter>())
          .Returns(Task.FromResult(new HttpResponseMessage { StatusCode = StatusCode.OK}));

// create the mock client factory mock
var httpClientFactoryMock = new Mock<IHttpClientFactory>();

// setup the method call
httpClientFactoryMock.Setup(x=>x.CreateClient(NamedHttpClients.COUCHDB))
                     .Returns(httpClient);

然后你必须将

httpClientFactoryMock.Object

传递给构造函数：

var messageHistoryService = new MessageHistoryService(httpClientFactoryMock.Object);

更新

为了进行单元测试

HttpClient

，因为它没有任何接口，您应该按照here中描述的方式包装它。

具体来说，我们必须如下安排http客户端：

// Mock the handler
var handlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);

handlerMock.Protected()
// Setup the PROTECTED method to mock
           .Setup<Task<HttpResponseMessage>>("PutAsync",
                                             ItExpr.IsAny<String>(),
                                             ItExpr.IsAny<Message>()
                                             ItExpr.IsAny<MediaTypeFormatter>())
// prepare the expected response of the mocked http call
           .ReturnsAsync(new HttpResponseMessage()
           {
               StatusCode = HttpStatusCode.OK
           })
           .Verifiable();

// use real http client with mocked handler here
var httpClient = new HttpClient(handlerMock.Object)
{
    BaseAddress = new Uri("http://test.com/"),
};

现在我们应该在调用

httpClient

时返回上面的

CreateClient

。

// create the mock client factory mock
var httpClientFactoryMock = new Mock<IHttpClientFactory>();

// setup the method call
httpClientFactoryMock.Setup(x=>x.CreateClient(NamedHttpClients.COUCHDB))
                     .Returns(httpClient);

Answer 2

自接受答案以来，IHttpMessageHandler 似乎已发生变化。在.NET6中它有2个方法“Send”和“SendAsync”。所以我修改了@Christos上面所做的，并将其放入静态类中以实现可重用性。

public static class MockHttpClient
{
    public static HttpClient GetHttpClient(HttpResponseMessage expectedResponse)
    {
        var handlerMock = new Mock<HttpMessageHandler>(MockBehavior.Strict);

        handlerMock.Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync(expectedResponse)
            .Verifiable();

        handlerMock.Protected()
            .Setup<HttpResponseMessage>("Send", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
            .Returns(expectedResponse)
            .Verifiable();

        return new HttpClient(handlerMock.Object);
    }
}

使用方法非常简单，不用创建Mock，直接实例化这个对象即可：

[SetUp]
public void SetUp()
{
    var _testResponse = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new StringContent("string response here"),
    };

    // Initialize the HttpClient mock
    _httpClientMock = MockHttpClient.GetHttpClient(_testResponse);
}

我上面的实现显然是返回一个字符串并响应任何方法（GET、POST、PUT 等...），但如果您需要具体，您可以修改它。