c# - 使用 Moq 的 ElasticClient 的代码覆盖率

Question

我正在尝试通过单元测试分析代码覆盖率，我目前正在使用 Moq 库执行单元测试，不知何故我走错了路，想知道以下场景是否适用于使用 Moq

下面是一段代码

public interface ISearchWorker
{
    void DeleteIndex(string indexName);

    T GetClient<T>();
}

public class ElasticSearchWorker : ISearchWorker
{
    public void DeleteIndex(string indexName)
    {
        IElasticClient elasticClient = GetClient<IElasticClient>();

        if (elasticClient.IndexExists(indexName).Exists)
        {
            _ = elasticClient.DeleteIndex(indexName);
        }
    }

    public T GetClient<T>()
    {        
        string nodeList = "http://localhost:9200/";

        List<Node> nodes = nodeList.Split(',').Select(uri => new Node(new Uri(uri))).ToList();

        IConnectionPool sniffingConnectionPool = new SniffingConnectionPool(nodes);

        IConnectionSettingsValues connectionSettings = new ConnectionSettings(sniffingConnectionPool);

        return (T)(IElasticClient)new ElasticClient(connectionSettings);        
    }
}

下面是单元测试的代码片段

    [TestClass]
    public class SearchTestClass
    {
        private ISearchWorker searchWorker;

        private Mock<ISearchWorker> searchWorkerMoq;

        private readonly string indexName = "testIndex";

        [TestInitialize]
        public void SetupElasticClient()
        {
            searchWorkerMoq = new Mock<ISearchWorker>();

            var elasticClient = new Mock<IElasticClient>();

            searchWorkerMoq.Setup(c => c.GetClient<IElasticClient>()).Returns(elasticClient.Object).Verifiable();

            searchWorker = searchWorkerMoq.Object;
        }

        [TestMethod]
        public void DeleteIndexTest()
        {
            try
            {
                searchWorker.DeleteIndex(indexName);

                searchWorkerMoq.Verify(c => c.GetClient<IElasticClient>(), Times.Once()); 
            }
            catch (System.Exception)
            {
                throw;
            }
        }
    }

线

searchWorkerMoq.Verify(c => c.GetClient<IElasticClient>(), Times.Once());

抛出以下异常

(Moq.MockException: '
Expected invocation on the mock once, but was 0 times: c => c.GetClient<IElasticClient>())

阅读大多数与 Moq 相关的信息，这似乎不是执行 Moq 测试的合适方式，IElasticClient 对象应在外部提供给 ElasticSearchWorker 类

不从外部注入(inject)提供 IElasticClient 对象的原因是我们计划为另一个搜索提供程序(Azure Search)实现 ISearchWorker，因此希望将客户端实体包含在实现 ISearchWorker 接口(interface)的类中

想知道是否有更好的方法来执行此测试，以及我们将如何实现此场景的代码覆盖率。

Answer 1

因此，我假设您理解为什么这不起作用，并且您只是在寻求解决此问题的“好方法”。

现在我并不是说这是最好的方法，但它可能是最快的，同时仍然是“干净的”。

应用界面隔离(SOLID 中的“I”)。制作两个接口(interface)而不是一个，然后在稍后阶段实现它们。

// Don't have a C# IDE with me, so sorry if I leave some syntax errors. 
public interface ISearchClientProvider
{
    T GetClient<T>();
}

public interface ISearchWorker
{
    void DeleteIndex(string indexName);
}

public class ElasticSearchWorker : ISearchWorker{

    private readonly ISearchClientProvider _clientProvider;

    public ElasticSearchWorker(ISearchClientProvider clientProvider){
        _clientProvider = clientProvider;
    }

    public void DeleteIndex(string indexName)
    {
        var elasticClient = _clientProvider.GetClient<IElasticClient>();

        if (elasticClient.IndexExists(indexName).Exists)
        {
            _ = elasticClient.DeleteIndex(indexName);
        }
    }
}

public class ElasticSearchClientProvider : ISearchClientProvider{/*some implementation*/}
public class AzureSearchWorker : ISearchWorker{/*some implementation*/}
public class AzureSearchClientProvider : ISearchClientProvider{/*some implementation*/}

那么测试代码应该是这样的:

// would actually prefer to name it ElasticSearchWorkerTests
[TestClass]
    public class SearchTestClass
    {
        private readonly ElasticSearchWorker _searchWorker;
        private readonly ISearchClientProvider _elasticClientProvider;

        private readonly string indexName = "testIndex";

        // would prefer to name it SetupElasticSearchWorker
        [TestInitialize]
        public void SetupElasticClient()
        {
            var elasticClient = new Mock<IElasticClient>();
            // Setup for IElasticClient.IndexExists() function:
            // I don't know what is the return type of IndexExists, 
            // so I am assuming here that it is some dynamic Object
            elasticClient.Setup(c => c.IndexExists(indexName)).Returns(new {Exists = true});
            // Setup for IElasticCleint.DeleteIndex might also be necessary here.

            _elasticClientProvider = new Mock<ISearchClientProvider>();
            _elasticClientProvider.Setup(c => c.GetClient<IElasticClient>()).Returns(elasticClient.Object).Verifiable();

            _searchWorker = new ElasticSearchWorker(_elasticClientProvider);
        }

        // would prefer to name it DeleteIndexTest_GetsSearchClient, 
        // because the function does more than is checked here, e.g., Checks index, deletes index.
        [TestMethod]
        public void DeleteIndexTest()
        {
            try
            {
                searchWorker.DeleteIndex(indexName);

                searchWorkerMoq.Verify(c => c.GetClient<IElasticClient>(), Times.Once()); 
            }
            catch (System.Exception)
            {
                throw;
            }
        }
    }

这样本次测试就没有http请求了。

一般来说(可以说是固执己见的部分)，如果您希望您的代码更具单元测试性:

使用Ports and Adapters (六边形，或者你想怎么称呼它)架构

经验法则。不要在其他公共(public)方法中调用公共(public)方法。使用composition解决这个问题。我在这个例子中使用了合成。

经验法则。不要在类中创建具有行为的对象。让您的composition root创建它们并将它们作为依赖项(接口(interface)的实现)注入(inject)到您的类中。如果无法在您的组合根目录中创建它们(也许您只在运行时知道您需要什么样的对象)，那么请使用工厂模式。

免责声明。您不需要 DI 容器即可使用组合根模式。您可以开始with poor man's DI .

总会有不可单元测试的类，因为来自 3rd 方的一些依赖项是不可模拟的。您的目标是制作这些类(class) very small然后与他们进行一些集成测试。 (我相信，测试覆盖率工具也会用到)

免责声明。我已经看到人们通过 HttpClientHandler 替换成功地模拟了 HttpClient。但是我还没有看到一个成功的 EF db 上下文模拟——它们都在某个时候失败了。

笔记。人们普遍认为您应该 not mock interfaces you do not own .所以，从这个意义上说，我上面的解决方案也不干净，将来可能会给你带来麻烦。