The number of shards used for indices created during integration tests is randomized between 1 and 10 unless overwritten upon index creation via index settings. The rule of thumb is not to specify the number of shards unless needed, so that each test will use a different one all the time. Alternatively you can override the numberOfShards() method. The same applies to the numberOfReplicas() method.

There are a couple of helper methods in ESIntegTestCase, which will make your tests shorter and more concise.

The InternalTestCluster class is the heart of the cluster functionality in a randomized test and allows you to configure a specific setting or replay certain types of outages to check, how your custom code reacts.

If you want to ensure a certain configuration for the nodes, which are started as part of the EsIntegTestCase, you can override the nodeSettings() method

public class Mytests extends ESIntegTestCase {

  @Override
  protected Settings nodeSettings(int nodeOrdinal) {
      return Settings.builder().put(super.nodeSettings(nodeOrdinal))
             .put("node.mode", "network")
             .build();
  }

}

In order to execute any actions, you have to use a client. You can use the ESIntegTestCase.client() method to get back a random client. This client can be a TransportClient or a NodeClient - and usually you do not need to care as long as the action gets executed. There are several more methods for client selection inside of the InternalTestCluster class, which can be accessed using the ESIntegTestCase.internalCluster() method.

By default the tests are run with unique cluster per test suite. Of course all indices and templates are deleted between each test. However, sometimes you need to start a new cluster for each test - for example, if you load a certain plugin, but you do not want to load it for every test.

You can use the @ClusterScope annotation at class level to configure this behaviour

@ClusterScope(scope=TEST, numDataNodes=1)
public class CustomSuggesterSearchTests extends ESIntegTestCase {
  // ... tests go here
}

The above sample configures the test to use a new cluster for each test method. The default scope is SUITE (one cluster for all test methods in the test). The numDataNodes settings allows you to only start a certain number of data nodes, which can speed up test execution, as starting a new node is a costly and time consuming operation and might not be needed for this test.

By default, the testing infrastructure will randomly start dedicated master nodes. If you want to disable dedicated masters you can set supportsDedicatedMasters=false in a similar fashion to the numDataNodes setting. If dedicated master nodes are not used, data nodes will be allowed to become masters as well.

As Elasticsearch is using JUnit 4, using the @Before and @After annotations is not a problem. However you should keep in mind, that this does not have any effect in your cluster setup, as the cluster is already up and running when those methods are run. So in case you want to configure settings - like loading a plugin on node startup - before the node is actually running, you should overwrite the nodePlugins() method from the ESIntegTestCase class and return the plugin classes each node should load.

@Override
protected Collection<Class<? extends Plugin>> nodePlugins() {
  return Arrays.asList(CustomSuggesterPlugin.class);
}