// create ES nodes
        final String clusterName = UUID.randomUUID().toString();
        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("http.cors.allow-origin", "*");
            settingsBuilder.put("discovery.type", "single-node");
        }).build(newConfigs().clusterName(clusterName).numOfNode(1));

        // wait for yellow status

        clusterName = response.getClusterName();
        clusterStatus = response.getStatus().toString();
        final Set<String> fieldSet = ComponentUtil.getFessConfig().getApiPingEsFieldSet();
        try (OutputStream out = SearchEngineUtil.getXContentBuilderOutputStream((builder, params) -> {
            builder.startObject();
            if (fieldSet.contains(CLUSTER_NAME)) {

    }

    /**
     * Set the value of clustername, used in parameter comment. <br>
     * Even if empty string, treated as empty plainly. So "IF pmb != null" is false if empty.
     * @param clustername The parameter value of clustername. (NotNull)
     */
    public void setClustername(String clustername) {
        registerVariable("clustername", clustername);
    }

    /**

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("ArraySettingsTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();
    }

    @AfterClass

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("ESSourceReaderTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();
    }

    @AfterClass

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("ArraySettingsTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();
    }

    @AfterClass

JUnit 4 with opensearch-runner (embedded instance)

### Standard Test Setup

```java
@BeforeClass
public static void beforeClass() {
    runner = new OpenSearchRunner();
    runner.build(newConfigs().clusterName("TestCluster").numOfNode(1));
    client = runner.client();
}

@Before
public void before() {
    runner.admin().indices().prepareDelete("_all").execute().actionGet();
}

@AfterClass

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("PopularWordsRequestBuilderTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();
    }

    @AfterClass

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("ArraySettingsTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();
    }

    @AfterClass

        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("discovery.type", "single-node");
        })
                .build(newConfigs().clusterName("DefaultNormalizerTest")
                        .numOfNode(1)
                        .pluginTypes("org.codelibs.opensearch.extension.ExtensionPlugin"));
        runner.ensureYellow();