fix(tests): prevent HashedWheelTimer leak in integration tests (#99)

  Integration test base classes in core/schema/jackson/client created a
  static HashedWheelTimer that was never released, emitting
  'LEAK: HashedWheelTimer.release() was not called' on every CI run.

  - Register a JVM shutdown hook that calls timer.stop() (static field
    shared per declaring class; @afterall would stop it after the first
    subclass and break the rest).
  - Extract the four inline hooks into a single TimerShutdownHook helper.
    Core + schema ship the helper in their own test sources; client and
    jackson copy it locally to avoid test-jar / package-phase dependency
    pitfalls seen with the original cross-module test-jar wiring.
  - IProtoClientTest.testTimeoutCancel: use a local timer so the cancel
    path is still covered without mutating the shared static.
  - IProtoClientWatchersTest.checkTTVersion: fall back to the actual
    container version when TARANTOOL_VERSION is unset (NPE on local runs).
    Drop a dead `version == null` ternary branch and rename
    testTimeoutCancel → testLocalTimerHasNoPending.

  Skipped: per-class try/finally around stop() to handle mid-test shutdown — add if a leak resurfaces under mvn
   -Pintegration.

Author: dkasimovskiy

tarantool-client/src/test/java/io/tarantool/client/integration/TarantoolCrudClientWithRetryTest.java

@@ -99,6 +99,10 @@ private void execute() {
   private static final Person personInstance = new Person(1, true, "Roman");
   private static final Timer timerService = new HashedWheelTimer();
 
+  static {
+    TimerShutdownHook.register(timerService, "tarantool-crud-client-retry-test-timer-shutdown");
+  }
+
   @BeforeAll
   public static void setUp() throws Exception {
     if (isCartridgeAvailable()) {

tarantool-client/src/test/java/io/tarantool/client/integration/TimerShutdownHook.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2026 VK DIGITAL TECHNOLOGIES LIMITED LIABILITY COMPANY
+ * All Rights Reserved.
+ */
+
+package io.tarantool.client.integration;
+
+import io.netty.util.Timer;
+
+public final class TimerShutdownHook {
+  private TimerShutdownHook() {}
+
+  public static void register(Timer timer, String name) {
+    Runtime.getRuntime().addShutdownHook(new Thread(timer::stop, name));
+  }
+}

tarantool-core/src/test/java/io/tarantool/core/integration/BaseTest.java

@@ -58,9 +58,13 @@ public abstract class BaseTest {
         }
       };
 
-  protected Timer timerService = new HashedWheelTimer();
+  protected static Timer timerService = new HashedWheelTimer();
 
-  protected ConnectionFactory factory = new ConnectionFactory(bootstrap, timerService);
+  protected static ConnectionFactory factory = new ConnectionFactory(bootstrap, timerService);
+
+  static {
+    TimerShutdownHook.register(timerService, "base-test-timer-shutdown");
+  }
 
   protected static ArrayValue decodeTuple(IProtoClient client, ArrayValue arrayValue)
       throws IOException {

tarantool-core/src/test/java/io/tarantool/core/integration/IProtoClientTest.java

@@ -28,6 +28,7 @@
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import io.netty.util.HashedWheelTimer;
+import io.netty.util.Timer;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeAll;
@@ -68,6 +69,7 @@
 import io.tarantool.core.IProtoClient;
 import io.tarantool.core.IProtoClientImpl;
 import io.tarantool.core.IProtoFeature;
+import io.tarantool.core.connection.ConnectionFactory;
 import io.tarantool.core.exceptions.BoxError;
 import io.tarantool.core.exceptions.BoxErrorStackItem;
 import io.tarantool.core.exceptions.ClientException;
@@ -1514,17 +1516,23 @@ public void testPing() throws Exception {
   }
 
   @Test
-  public void testTimeoutCancel() throws Exception {
-    IProtoClient client = createClientAndConnect(address, true);
+  public void testLocalTimerHasNoPending() throws Exception {
+    Timer localTimer = new HashedWheelTimer();
+    IProtoClient client =
+        new IProtoClientImpl(
+            new ConnectionFactory(bootstrap, localTimer),
+            localTimer,
+            DEFAULT_WATCHER_OPTS,
+            null,
+            null,
+            true);
+    client.connect(address, 3_000).get();
     client.authorize(API_USER, CREDS.get(API_USER)).join();
     IProtoMessage message = client.ping().get();
     checkMessageHeader(message, IPROTO_OK, 4);
     assertEquals(0, message.getBody().map().size());
 
-    Set<io.netty.util.Timeout> timers = timerService.stop();
-    assertTrue(timers.isEmpty());
-
-    timerService = new HashedWheelTimer();
+    assertTrue(localTimer.stop().isEmpty());
   }
 
   @Test

tarantool-core/src/test/java/io/tarantool/core/integration/TimerShutdownHook.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2026 VK DIGITAL TECHNOLOGIES LIMITED LIABILITY COMPANY
+ * All Rights Reserved.
+ */
+
+package io.tarantool.core.integration;
+
+import io.netty.util.Timer;
+
+public final class TimerShutdownHook {
+  private TimerShutdownHook() {}
+
+  public static void register(Timer timer, String name) {
+    Runtime.getRuntime().addShutdownHook(new Thread(timer::stop, name));
+  }
+}

tarantool-jackson-mapping/src/test/java/io/tarantool/mapping/integration/BaseTest.java

@@ -47,4 +47,8 @@ public abstract class BaseTest {
           .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 3000);
   protected static final Timer timerService = new HashedWheelTimer();
   protected static final ConnectionFactory factory = new ConnectionFactory(bootstrap, timerService);
+
+  static {
+    TimerShutdownHook.register(timerService, "jackson-mapping-base-test-timer-shutdown");
+  }
 }

tarantool-jackson-mapping/src/test/java/io/tarantool/mapping/integration/TimerShutdownHook.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2026 VK DIGITAL TECHNOLOGIES LIMITED LIABILITY COMPANY
+ * All Rights Reserved.
+ */
+
+package io.tarantool.mapping.integration;
+
+import io.netty.util.Timer;
+
+public final class TimerShutdownHook {
+  private TimerShutdownHook() {}
+
+  public static void register(Timer timer, String name) {
+    Runtime.getRuntime().addShutdownHook(new Thread(timer::stop, name));
+  }
+}

tarantool-schema/src/test/java/io/tarantool/client/integration/TarantoolSchemaFetcherTest.java

@@ -75,6 +75,10 @@ public class TarantoolSchemaFetcherTest {
   private static final Timer timerService = new HashedWheelTimer();
   private static final ConnectionFactory factory = new ConnectionFactory(bootstrap, timerService);
 
+  static {
+    TimerShutdownHook.register(timerService, "tarantool-schema-fetcher-test-timer-shutdown");
+  }
+
   private static TarantoolContainer<?> tt;
 
   private Long spacePersonId;

tarantool-schema/src/test/java/io/tarantool/client/integration/TimerShutdownHook.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2026 VK DIGITAL TECHNOLOGIES LIMITED LIABILITY COMPANY
+ * All Rights Reserved.
+ */
+
+package io.tarantool.client.integration;
+
+import io.netty.util.Timer;
+
+public final class TimerShutdownHook {
+  private TimerShutdownHook() {}
+
+  public static void register(Timer timer, String name) {
+    Runtime.getRuntime().addShutdownHook(new Thread(timer::stop, name));
+  }
+}