diff --git a/build.gradle b/build.gradle
index df2dfa7..5273aa6 100644
--- a/build.gradle
+++ b/build.gradle
@@ -65,7 +65,7 @@ subprojects {
     }
 
     test {
-        enabled = false
+        enabled = true
         useJUnitPlatform()
         // we MUST use this hack because of Elasticsearch 2.2.1 Lucene 5.4.1 MMapDirectory unmap() hackery
         doFirst {
diff --git a/elx-common/src/main/java/org/xbib/elx/common/DefaultBulkProcessor.java b/elx-common/src/main/java/org/xbib/elx/common/DefaultBulkProcessor.java
index c633ad1..74915c9 100644
--- a/elx-common/src/main/java/org/xbib/elx/common/DefaultBulkProcessor.java
+++ b/elx-common/src/main/java/org/xbib/elx/common/DefaultBulkProcessor.java
@@ -20,8 +20,6 @@ import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
-import java.util.logging.Level;
-import java.util.logging.Logger;
 
 /**
  * A bulk processor is a thread safe bulk processing class, allowing to easily set when to "flush" a new bulk request
@@ -31,8 +29,6 @@ import java.util.logging.Logger;
  */
 public class DefaultBulkProcessor implements BulkProcessor {
 
-    private static final Logger logger = Logger.getLogger(DefaultBulkProcessor.class.getName());
-
     private final int bulkActions;
 
     private final long bulkSize;
@@ -56,9 +52,6 @@ public class DefaultBulkProcessor implements BulkProcessor {
         this.bulkActions = bulkActions;
         this.bulkSize = bulkSize.getBytes();
         this.bulkRequest = new BulkRequest();
-        if (listener == null) {
-            throw new IllegalArgumentException();
-        }
         this.bulkRequestHandler = concurrentRequests == 0 ?
                 new SyncBulkRequestHandler(client, listener) :
                 new AsyncBulkRequestHandler(client, listener, concurrentRequests);
@@ -76,9 +69,8 @@ public class DefaultBulkProcessor implements BulkProcessor {
     }
 
     public static Builder builder(ElasticsearchClient client, Listener listener) {
-        if (client == null) {
-            throw new NullPointerException("The client you specified while building a BulkProcessor is null");
-        }
+        Objects.requireNonNull(client, "The client you specified while building a BulkProcessor is null");
+        Objects.requireNonNull(listener, "A listener for the BulkProcessor is required but null");
         return new Builder(client, listener);
     }
 
@@ -91,6 +83,7 @@ public class DefaultBulkProcessor implements BulkProcessor {
      */
     @Override
     public synchronized boolean awaitFlush(long timeout, TimeUnit unit) throws InterruptedException {
+        Objects.requireNonNull(unit, "A time unit is required for awaitFlush() but null");
         if (closed) {
             return true;
         }
@@ -99,7 +92,7 @@ public class DefaultBulkProcessor implements BulkProcessor {
             execute();
         }
         // wait for all bulk responses
-        return this.bulkRequestHandler.close(timeout, unit);
+        return bulkRequestHandler.close(timeout, unit);
     }
 
     /**
@@ -119,18 +112,19 @@ public class DefaultBulkProcessor implements BulkProcessor {
      */
     @Override
     public synchronized boolean awaitClose(long timeout, TimeUnit unit) throws InterruptedException {
+        Objects.requireNonNull(unit, "A time unit is required for awaitCLose() but null");
         if (closed) {
             return true;
         }
         closed = true;
-        if (this.scheduledFuture != null) {
-            FutureUtils.cancel(this.scheduledFuture);
-            this.scheduler.shutdown();
+        if (scheduledFuture != null) {
+            FutureUtils.cancel(scheduledFuture);
+            scheduler.shutdown();
         }
         if (bulkRequest.numberOfActions() > 0) {
             execute();
         }
-        return this.bulkRequestHandler.close(timeout, unit);
+        return bulkRequestHandler.close(timeout, unit);
     }
 
     /**
@@ -213,8 +207,7 @@ public class DefaultBulkProcessor implements BulkProcessor {
     private boolean isOverTheLimit() {
         return bulkActions != -1 &&
                 bulkRequest.numberOfActions() >= bulkActions ||
-                bulkSize != -1 &&
-                        bulkRequest.estimatedSizeInBytes() >= bulkSize;
+                bulkSize != -1 && bulkRequest.estimatedSizeInBytes() >= bulkSize;
     }
 
     /**
@@ -342,6 +335,7 @@ public class DefaultBulkProcessor implements BulkProcessor {
         private final DefaultBulkProcessor.Listener listener;
 
         SyncBulkRequestHandler(ElasticsearchClient client, DefaultBulkProcessor.Listener listener) {
+            Objects.requireNonNull(listener, "A listener is required for SyncBulkRequestHandler but null");
             this.client = client;
             this.listener = listener;
         }
@@ -378,6 +372,7 @@ public class DefaultBulkProcessor implements BulkProcessor {
         private final int concurrentRequests;
 
         private AsyncBulkRequestHandler(ElasticsearchClient client, DefaultBulkProcessor.Listener listener, int concurrentRequests) {
+            Objects.requireNonNull(listener, "A listener is required for AsyncBulkRequestHandler but null");
             this.client = client;
             this.listener = listener;
             this.concurrentRequests = concurrentRequests;
@@ -426,10 +421,6 @@ public class DefaultBulkProcessor implements BulkProcessor {
 
         @Override
         public boolean close(long timeout, TimeUnit unit) throws InterruptedException {
-            logger.log(Level.INFO, "semaphore=" + semaphore +
-                    " concurrentRequests=" + concurrentRequests +
-                    " timeout=" + timeout +
-                    " unit=" + unit);
             if (semaphore.tryAcquire(concurrentRequests, timeout, unit)) {
                 semaphore.release(concurrentRequests);
                 return true;
diff --git a/elx-common/src/test/java/org/xbib/elx/common/test/TestExtension.java b/elx-common/src/test/java/org/xbib/elx/common/test/TestExtension.java
index fdf65e6..6186f8c 100644
--- a/elx-common/src/test/java/org/xbib/elx/common/test/TestExtension.java
+++ b/elx-common/src/test/java/org/xbib/elx/common/test/TestExtension.java
@@ -19,8 +19,8 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.transport.InetSocketTransportAddress;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.node.Node;
-import org.junit.jupiter.api.extension.AfterAllCallback;
-import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
 import org.junit.jupiter.api.extension.ParameterResolutionException;
@@ -39,7 +39,7 @@ import java.util.Random;
 
 import static org.elasticsearch.common.settings.Settings.settingsBuilder;
 
-public class TestExtension implements ParameterResolver, BeforeAllCallback, AfterAllCallback {
+public class TestExtension implements ParameterResolver, BeforeEachCallback, AfterEachCallback {
 
     private static final Logger logger = LogManager.getLogger("test");
 
@@ -73,18 +73,15 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     @Override
     public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
             throws ParameterResolutionException {
+        setHome(System.getProperty("path.home") + "/" + getRandomString(8));
+        setClusterName("test-cluster-" + System.getProperty("user.name"));
         return extensionContext.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create());
     }
 
     @Override
-    public void beforeAll(ExtensionContext context) throws Exception {
+    public void beforeEach(ExtensionContext context) throws Exception {
         Helper helper = context.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create(), Helper.class);
-        setHome(System.getProperty("path.home") + "/" + helper.randomString(8));
-        setClusterName("test-cluster-" + System.getProperty("user.name"));
         logger.info("starting cluster");
-        deleteFiles(Paths.get(getHome() + "/data"));
-        logger.info("data files wiped");
-        Thread.sleep(2000L); // let OS commit changes
         helper.startNode("1");
         NodesInfoRequest nodesInfoRequest = new NodesInfoRequest().transport(true);
         NodesInfoResponse response = helper.client("1"). execute(NodesInfoAction.INSTANCE, nodesInfoRequest).actionGet();
@@ -114,9 +111,11 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     }
 
     @Override
-    public void afterAll(ExtensionContext context) throws Exception {
+    public void afterEach(ExtensionContext context) throws Exception {
         closeNodes();
         deleteFiles(Paths.get(getHome() + "/data"));
+        logger.info("data files wiped");
+        Thread.sleep(2000L); // let OS commit changes
     }
 
     private void setClusterName(String cluster) {
@@ -169,6 +168,15 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
         }
     }
 
+    private String getRandomString(int len) {
+        final char[] buf = new char[len];
+        final int n = numbersAndLetters.length - 1;
+        for (int i = 0; i < buf.length; i++) {
+            buf[i] = numbersAndLetters[random.nextInt(n)];
+        }
+        return new String(buf);
+    }
+
     private Helper create() {
         return new Helper();
     }
@@ -186,6 +194,14 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             buildNode(id).start();
         }
 
+        ElasticsearchClient client(String id) {
+            return clients.get(id);
+        }
+
+        String randomString(int n) {
+            return getRandomString(n);
+        }
+
         private Node buildNode(String id) {
             Settings nodeSettings = settingsBuilder()
                     .put(getNodeSettings())
@@ -198,19 +214,5 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             logger.info("clients={}", clients);
             return node;
         }
-
-        String randomString(int len) {
-            final char[] buf = new char[len];
-            final int n = numbersAndLetters.length - 1;
-            for (int i = 0; i < buf.length; i++) {
-                buf[i] = numbersAndLetters[random.nextInt(n)];
-            }
-            return new String(buf);
-        }
-
-        ElasticsearchClient client(String id) {
-            return clients.get(id);
-        }
-
     }
 }
diff --git a/elx-node/src/test/java/org/xbib/elx/node/test/SmokeTest.java b/elx-node/src/test/java/org/xbib/elx/node/test/SmokeTest.java
index ae33bd9..c9a7cd7 100644
--- a/elx-node/src/test/java/org/xbib/elx/node/test/SmokeTest.java
+++ b/elx-node/src/test/java/org/xbib/elx/node/test/SmokeTest.java
@@ -44,7 +44,7 @@ class SmokeTest {
             client.waitForRecovery("test_smoke", 10L, TimeUnit.SECONDS);
             client.delete("test_smoke", "1");
             client.deleteIndex("test_smoke");
-            IndexDefinition indexDefinition = client.buildIndexDefinitionFromSettings("test_smoke", Settings.settingsBuilder()
+            IndexDefinition indexDefinition = client.buildIndexDefinitionFromSettings("test_smoke_2", Settings.settingsBuilder()
                     .build());
             assertEquals(0, indexDefinition.getReplicaLevel());
             client.newIndex(indexDefinition);
diff --git a/elx-node/src/test/java/org/xbib/elx/node/test/TestExtension.java b/elx-node/src/test/java/org/xbib/elx/node/test/TestExtension.java
index 7d28686..dcd0e31 100644
--- a/elx-node/src/test/java/org/xbib/elx/node/test/TestExtension.java
+++ b/elx-node/src/test/java/org/xbib/elx/node/test/TestExtension.java
@@ -19,8 +19,8 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.transport.InetSocketTransportAddress;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.node.Node;
-import org.junit.jupiter.api.extension.AfterAllCallback;
-import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
 import org.junit.jupiter.api.extension.ParameterResolutionException;
@@ -39,7 +39,7 @@ import java.util.Random;
 
 import static org.elasticsearch.common.settings.Settings.settingsBuilder;
 
-public class TestExtension implements ParameterResolver, BeforeAllCallback, AfterAllCallback {
+public class TestExtension implements ParameterResolver, BeforeEachCallback, AfterEachCallback {
 
     private static final Logger logger = LogManager.getLogger("test");
 
@@ -73,17 +73,14 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     @Override
     public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
             throws ParameterResolutionException {
+        setHome(System.getProperty("path.home") + "/" + getRandomString(8));
+        setClusterName("test-cluster-" + System.getProperty("user.name"));
         return extensionContext.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create());
     }
 
     @Override
-    public void beforeAll(ExtensionContext context) throws Exception {
+    public void beforeEach(ExtensionContext context) throws Exception {
         Helper helper = context.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create(), Helper.class);
-        setHome(System.getProperty("path.home") + "/" + helper.randomString(8));
-        setClusterName("test-cluster-" + System.getProperty("user.name"));
-        deleteFiles(Paths.get(getHome() + "/data"));
-        logger.info("data files wiped");
-        Thread.sleep(2000L); // let OS commit changes
         logger.info("starting cluster");
         helper.startNode("1");
         NodesInfoRequest nodesInfoRequest = new NodesInfoRequest().transport(true);
@@ -114,9 +111,11 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     }
 
     @Override
-    public void afterAll(ExtensionContext context) throws Exception {
+    public void afterEach(ExtensionContext context) throws Exception {
         closeNodes();
         deleteFiles(Paths.get(getHome() + "/data"));
+        logger.info("data files wiped");
+        Thread.sleep(2000L); // let OS commit changes
     }
 
     private void setClusterName(String cluster) {
@@ -169,6 +168,15 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
         }
     }
 
+    private String getRandomString(int len) {
+        final char[] buf = new char[len];
+        final int n = numbersAndLetters.length - 1;
+        for (int i = 0; i < buf.length; i++) {
+            buf[i] = numbersAndLetters[random.nextInt(n)];
+        }
+        return new String(buf);
+    }
+
     private Helper create() {
         return new Helper();
     }
@@ -179,6 +187,18 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             buildNode(id).start();
         }
 
+        ElasticsearchClient client(String id) {
+            return clients.get(id);
+        }
+
+        String getCluster() {
+            return getClusterName();
+        }
+
+        String randomString(int n) {
+            return getRandomString(n);
+        }
+
         private Node buildNode(String id) {
             Settings nodeSettings = settingsBuilder()
                     .put("cluster.name", getClusterName())
@@ -192,22 +212,5 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             logger.info("clients={}", clients);
             return node;
         }
-
-        String randomString(int len) {
-            final char[] buf = new char[len];
-            final int n = numbersAndLetters.length - 1;
-            for (int i = 0; i < buf.length; i++) {
-                buf[i] = numbersAndLetters[random.nextInt(n)];
-            }
-            return new String(buf);
-        }
-
-        ElasticsearchClient client(String id) {
-            return clients.get(id);
-        }
-
-        String getCluster() {
-            return getClusterName();
-        }
     }
 }
diff --git a/elx-transport/src/test/java/org/xbib/elx/transport/test/ClientTest.java b/elx-transport/src/test/java/org/xbib/elx/transport/test/ClientTest.java
index 54b68c5..73c0f81 100644
--- a/elx-transport/src/test/java/org/xbib/elx/transport/test/ClientTest.java
+++ b/elx-transport/src/test/java/org/xbib/elx/transport/test/ClientTest.java
@@ -13,7 +13,6 @@ import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.index.query.QueryBuilders;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.xbib.elx.common.ClientBuilder;
@@ -43,7 +42,6 @@ class ClientTest {
 
     ClientTest(TestExtension.Helper helper) {
         this.helper = helper;
-        helper.startNode("2");
     }
 
     @Test
@@ -145,7 +143,6 @@ class ClientTest {
     }
 
     @Test
-    @Disabled
     void testThreadedRandomDocs() throws Exception {
         int maxthreads = Runtime.getRuntime().availableProcessors();
         long maxactions = MAX_ACTIONS_PER_REQUEST;
diff --git a/elx-transport/src/test/java/org/xbib/elx/transport/test/DuplicateIDTest.java b/elx-transport/src/test/java/org/xbib/elx/transport/test/DuplicateIDTest.java
index 8172f89..64207e7 100644
--- a/elx-transport/src/test/java/org/xbib/elx/transport/test/DuplicateIDTest.java
+++ b/elx-transport/src/test/java/org/xbib/elx/transport/test/DuplicateIDTest.java
@@ -25,9 +25,9 @@ class DuplicateIDTest {
 
     private final static Logger logger = LogManager.getLogger(DuplicateIDTest.class.getName());
 
-    private final static Long MAX_ACTIONS_PER_REQUEST = 10L;
+    private final static Long MAX_ACTIONS_PER_REQUEST = 100L;
 
-    private final static Long ACTIONS = 5L;
+    private final static Long ACTIONS = 50L;
 
     private final TestExtension.Helper helper;
 
diff --git a/elx-transport/src/test/java/org/xbib/elx/transport/test/IndexShiftTest.java b/elx-transport/src/test/java/org/xbib/elx/transport/test/IndexShiftTest.java
index 1c57312..1f65064 100644
--- a/elx-transport/src/test/java/org/xbib/elx/transport/test/IndexShiftTest.java
+++ b/elx-transport/src/test/java/org/xbib/elx/transport/test/IndexShiftTest.java
@@ -33,7 +33,7 @@ class IndexShiftTest {
     }
 
     @Test
-    void testIndexAlias() throws Exception {
+    void testIndexShift() throws Exception {
         final ExtendedTransportClient client = ClientBuilder.builder()
                 .provider(ExtendedTransportClientProvider.class)
                 .put(helper.getTransportSettings()).build();
diff --git a/elx-transport/src/test/java/org/xbib/elx/transport/test/SmokeTest.java b/elx-transport/src/test/java/org/xbib/elx/transport/test/SmokeTest.java
index 0572ef5..be4a87b 100644
--- a/elx-transport/src/test/java/org/xbib/elx/transport/test/SmokeTest.java
+++ b/elx-transport/src/test/java/org/xbib/elx/transport/test/SmokeTest.java
@@ -45,7 +45,7 @@ class SmokeTest extends TestExtension {
             client.waitForRecovery("test_smoke", 10L, TimeUnit.SECONDS);
             client.delete("test_smoke", "1");
             client.deleteIndex("test_smoke");
-            IndexDefinition indexDefinition = client.buildIndexDefinitionFromSettings("test2", Settings.settingsBuilder()
+            IndexDefinition indexDefinition = client.buildIndexDefinitionFromSettings("test_smoke_2", Settings.settingsBuilder()
                     .build());
             assertEquals(0, indexDefinition.getReplicaLevel());
             client.newIndex(indexDefinition);
diff --git a/elx-transport/src/test/java/org/xbib/elx/transport/test/TestExtension.java b/elx-transport/src/test/java/org/xbib/elx/transport/test/TestExtension.java
index 8c6fe19..e37ca8c 100644
--- a/elx-transport/src/test/java/org/xbib/elx/transport/test/TestExtension.java
+++ b/elx-transport/src/test/java/org/xbib/elx/transport/test/TestExtension.java
@@ -19,8 +19,8 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.transport.InetSocketTransportAddress;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.node.Node;
-import org.junit.jupiter.api.extension.AfterAllCallback;
-import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
 import org.junit.jupiter.api.extension.ParameterResolutionException;
@@ -39,7 +39,7 @@ import java.util.Random;
 
 import static org.elasticsearch.common.settings.Settings.settingsBuilder;
 
-public class TestExtension implements ParameterResolver, BeforeAllCallback, AfterAllCallback {
+public class TestExtension implements ParameterResolver, BeforeEachCallback, AfterEachCallback {
 
     private static final Logger logger = LogManager.getLogger("test");
 
@@ -59,7 +59,7 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
 
     private int port;
 
-    private static final String key = "es-instance";
+    private static final String key = "es-test-instance";
 
     private static final ExtensionContext.Namespace ns =
             ExtensionContext.Namespace.create(TestExtension.class);
@@ -73,17 +73,14 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     @Override
     public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext)
             throws ParameterResolutionException {
-        return extensionContext.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create());
+        setHome(System.getProperty("path.home") + "/" + getRandomString(8));
+        setClusterName("test-cluster-" + System.getProperty("user.name"));
+        return extensionContext.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create(), Helper.class);
     }
 
     @Override
-    public void beforeAll(ExtensionContext context) throws Exception {
-        Helper helper = context.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create(), Helper.class);
-        setHome(System.getProperty("path.home") + "/" + helper.randomString(8));
-        setClusterName("test-cluster-" + System.getProperty("user.name"));
-        deleteFiles(Paths.get(getHome() + "/data"));
-        logger.info("data files wiped: " + getHome());
-        Thread.sleep(2000L); // let OS commit changes
+    public void beforeEach(ExtensionContext extensionContext) throws Exception {
+        Helper helper = extensionContext.getParent().get().getStore(ns).getOrComputeIfAbsent(key, key -> create(), Helper.class);
         logger.info("starting cluster");
         helper.startNode("1");
         NodesInfoRequest nodesInfoRequest = new NodesInfoRequest().transport(true);
@@ -114,10 +111,11 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
     }
 
     @Override
-    public void afterAll(ExtensionContext context) throws Exception {
+    public void afterEach(ExtensionContext context) throws Exception {
         closeNodes();
         deleteFiles(Paths.get(getHome() + "/data"));
-        logger.info("cluster stopped");
+        logger.info("data files wiped: " + getHome());
+        Thread.sleep(2000L); // let OS commit changes
     }
 
     private void setClusterName(String cluster) {
@@ -170,6 +168,15 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
         }
     }
 
+    private String getRandomString(int len) {
+        final char[] buf = new char[len];
+        final int n = numbersAndLetters.length - 1;
+        for (int i = 0; i < buf.length; i++) {
+            buf[i] = numbersAndLetters[random.nextInt(n)];
+        }
+        return new String(buf);
+    }
+
     private Helper create() {
         return new Helper();
     }
@@ -196,6 +203,18 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             buildNode(id).start();
         }
 
+        ElasticsearchClient client(String id) {
+            return clients.get(id);
+        }
+
+        String getCluster() {
+            return getClusterName();
+        }
+
+        String randomString(int n) {
+            return getRandomString(n);
+        }
+
         private Node buildNode(String id) {
             Settings nodeSettings = settingsBuilder()
                     .put(getNodeSettings())
@@ -208,22 +227,5 @@ public class TestExtension implements ParameterResolver, BeforeAllCallback, Afte
             logger.info("clients={}", clients);
             return node;
         }
-
-        String randomString(int len) {
-            final char[] buf = new char[len];
-            final int n = numbersAndLetters.length - 1;
-            for (int i = 0; i < buf.length; i++) {
-                buf[i] = numbersAndLetters[random.nextInt(n)];
-            }
-            return new String(buf);
-        }
-
-        ElasticsearchClient client(String id) {
-            return clients.get(id);
-        }
-
-        String getCluster() {
-            return getClusterName();
-        }
     }
 }