尝试在 Mockito 中模拟 ElasticClient 时出现 NPE 错误

Question

我是 Mockito 框架的新手，我正在为包含 ElasticClient 的 class 编写测试。下面是我的实际方法：

@Service
@Slf4j
public class CreateIndex {

    private final RestHighLevelClient elasticClient;

    @Autowired
    public IndexService(final RestHighLevelClient elasticClient) throws IOException {
        this.elasticClient = elasticClient;
    }

    public boolean createIndex(String id, String index) {
        try {
            IndexRequest request = new IndexRequest(index);
            request.id(id);
            elasticClient.index(request, RequestOptions.DEFAULT);
            return true;
        } catch (IOException e) {
            log.warn(e.getMessage());
        }
        return false;
    }

我的测试代码是这样的：

public class TestCreateIndex {
   CreateIndex createIndex;
    @Mock
    RestHighLevelClient elasticClient;
    @Rule
    public MockitoRule rule = MockitoJUnit.rule();
    @Before
    public void before() throws IOException {
        createIndex = new CreateIndex(elasticClient);
    }

@Test
    public void TestCreateIndex() throws IOException {
            IndexRequest request = new IndexRequest("1");
            request.id("1");
            Mockito.when(elasticClient.index(request,(RequestOptions.DEFAULT))).thenReturn(indexResponse);

    }
}

对于行 Mockito.when(elasticClient.index(request,RequestOptions.DEFAULT )).thenReturn(indexResponse);（RequestOptions 是一些 Class），我遇到以下错误：

java.lang.NullPointerException: Cannot invoke "org.elasticsearch.client.RestClient.performRequest(org.elasticsearch.client.Request)" because "this.client" is null

    at org.elasticsearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1514)
    at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1484)
    at org.elasticsearch.client.RestHighLevelClient.performRequestAndParseEntity(RestHighLevelClient.java:1454)
    at org.elasticsearch.client.RestHighLevelClient.index(RestHighLevelClient.java:871)

不确定，如何正确模拟 elasticClient。请帮忙。

Answer 1

问题是您尝试存根的方法是最终方法：

public final IndexResponse index(IndexRequest indexRequest, 
                                 RequestOptions options) throws IOException

Mockito 不支持开箱即用的模拟 final 方法，相反，它调用真正的方法，这会导致 NPE，因为 private final RestClient client; 未初始化。

幸运的是，stubbing final 方法可以很容易地添加为配置选项。参见 Mock Final Classes and Methods with Mockito

Before Mockito can be used for mocking final classes and methods, it needs to be configured.

We need to add a text file to the project's src/test/resources/mockito-extensions directory named org.mockito.plugins.MockMaker and add a single line of text:

mock-maker-inline

Mockito checks the extensions directory for configuration files when it is loaded. This file enables the mocking of final methods and classes.

或者，从 mockito 2.7.6 开始，您可以使用 mockito-inline 工件（而不是 mockito-core）来启用内联模拟制作

尝试在 Mockito 中模拟 ElasticClient 时出现 NPE 错误

Getting NPE error when trying to mock ElasticClient in Mockito

java

junit

unit-testing

mockito

elasticsearch