NullPointerException Problem when trying to mock Elastic Search's RestHighLevelClient

Question

I'm facing a NullPointerException during unit testing, when trying to test and mock a RestHighLevelClient inside an ElasticClient class:

@Configuration
@NoArgsConstructor
public class ElasticClient{

   @Setter
   private RestHighLevelClient restHighLevelClient;

    @PostConstruct
    public void buildRestHighLevelClient(){

        RestClientBuilder restClientBuilder = RestClient.builder(new HttpHost(
                "127.0.0.1",
                9200, "http")
        );

        restClientBuilder.setRequestConfigCallback(
                requestConfigBuilder ->
                        requestConfigBuilder
                                .setConnectTimeout(500000)
                                .setSocketTimeout(600000)
                                .setConnectionRequestTimeout(0)
        )
                .setHttpClientConfigCallback(
                        httpClientBuilder ->
                                httpClientBuilder
                                        .setMaxConnPerRoute(2048)
                );

        restHighLevelClient = new RestHighLevelClient(restClientBuilder);
    }

   public boolean isReachable(){
     return restHighLevelClient.ping(RequestOptions.DEFAULT);
   }

}

And the test class:

@RunWith(MockitoJUnitRunner.class)
@SpringBootTest
public class ElasticClientTest{

@Mock
private RestHighLevelClient restHighLevelClient;


ElasticClient elasticClient;

@Before
public void init(){

    elasticClient = new ElasticClient();
    elasticClient.setRestHighLevelClient(restHighLevelClient);

}

And the NullPointerException is coming from here:

    @Test
    public void whenElasticIsPingable_thenReturnTrue() throws IOException{

           when(restHighLevelClient.ping(RequestOptions.DEFAULT)).thenReturn(true);
           Assertions.assertThat(elasticClient.isReachable()).isTrue();
    }

Here is the stacktrace:

java.lang.NullPointerException
at org.elasticsearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1764)
at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1734)
at org.elasticsearch.client.RestHighLevelClient.ping(RestHighLevelClient.java:694)
at com.example.ElasticClientTest.whenElasticIsPingable_thenReturnTrue(ElasticClientTest.java:44)

is this `RestHighLevelClient` Autowired in `ElasticClient` ?, can you show complete class of `ElasticClient` — Ryuzaki L, Nov 18 '19 at 13:03
[`restHighLevelClient.ping`](https://github.com/elastic/elasticsearch/blob/master/client/rest-high-level/src/main/java/org/elasticsearch/client/RestHighLevelClient.java#L719) is a `final` method. Did you enable mockito to handle `final` as mentioned in the [docu](https://javadoc.io/static/org.mockito/mockito-core/3.1.0/org/mockito/Mockito.html#39) ? — second, Nov 18 '19 at 14:27

score 3 · Accepted Answer · answered Nov 18 '19 at 14:30

The problem is originated from the fact that the ping method in the RestHighLevelClient is final as can't be mocked regularly.

So, I used the help of this example about PowerMock

And in the final result:

@RunWith(PowerMockRunner.class)
@PrepareForTest(RestHighLevelClient.class)
public class ElasticClientTest{

ElasticClient elasticClient;

RestHighLevelClient restHighLevelClient;

@Before
public void init(){

    restHighLevelClient = mock(RestHighLevelClient.class);

    elasticClient = new ElasticClient();
    elasticClient.setRestHighLevelClient(restHighLevelClient);

}


@Test
public void whenElasticIsPingable_thenReturnTrue() throws IOException{

    when(restHighLevelClient.ping(RequestOptions.DEFAULT)).thenReturn(true);

    Assertions.assertThat(elasticClient.isReachable()).isTrue();
}

score 1 · Answer 2 · answered Feb 04 '22 at 13:08

You need to add a mockito extension for mock a finalized object with these steps:

Create a folder called "mockito-extensions" in test resources folder.
Add a file called "org.mockito.plugins.MockMaker" inside the folder.
In that file, write "mock-maker-inline"

score 0 · Answer 3 · edited Nov 18 '19 at 15:06

0

Try:

when(restHighLevelClient.ping(eq(RequestOptions.DEFAULT))).thenReturn(true);

edited Nov 18 '19 at 15:06

double-beep

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answered Nov 18 '19 at 12:16

Ahmed HENTETI

1,108
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With the same stacktrace ? Which `eq` method are you importing ? – Ahmed HENTETI Nov 18 '19 at 12:28
The error is a bit different - `You cannot use argument matchers outside of verification or stubbing` and `java.lang.NullPointerException: options cannot be null at java.util.Objects.requireNonNull(Objects.java:228) at org.elasticsearch.client.Request.setOptions(Request.java:126) at org.elasticsearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1761) at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1734) at org.elasticsearch.client.RestHighLevelClient.ping(RestHighLevelClient.java:694)` – riorio Nov 18 '19 at 12:47
import static org.mockito.Mockito.eq; – riorio Nov 18 '19 at 12:47
The import statement is OK. Can you please run your test without the `@SpringBootTest` to see if it is the root cause of this problem (I'm not sûre) – Ahmed HENTETI Nov 18 '19 at 13:08
same result when removing the `@SpringBootTest` – riorio Nov 18 '19 at 13:14

NullPointerException Problem when trying to mock Elastic Search's RestHighLevelClient

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