*
     * @param manager channel manager
     */
    public ChannelFailover(ChannelManager manager) {
        this.manager = manager;
        this.executor = Executors.newCachedThreadPool(r -> {
            Thread t = new Thread(r, "MultiChannelFailover");
            t.setDaemon(true);
            return t;
        });
        this.failoverStates = new ConcurrentHashMap<>();
    }

    /**
     * Handle channel failure
     *

    }

    /**
     * Test that pre-auth integrity hash is properly synchronized
     */
    @Test
    @DisplayName("Pre-auth integrity hash should be thread-safe")
    void testPreauthHashThreadSafety() throws Exception {
        // Setup SMB3.1.1 negotiation
        when(negotiateResponse.getSelectedDialect()).thenReturn(DialectVersion.SMB311);

                org.codelibs.core.timer.TimeoutTask accessTimeoutTask = null;
                if (accessTimeout != null) {
                    accessTimeoutTarget = new org.codelibs.fess.crawler.client.AccessTimeoutTarget(Thread.currentThread());
                    accessTimeoutTask = org.codelibs.core.timer.TimeoutManager.getInstance()
                            .addTimeoutTarget(accessTimeoutTarget, accessTimeout, false);
                }

            while (crawler.crawlerContext.getStatus() != CrawlerStatus.RUNNING && System.currentTimeMillis() - startTime < 5000) {
                try {
                    Thread.sleep(50);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    break;
                }
            }
            assertEquals(CrawlerStatus.RUNNING, crawler.crawlerContext.getStatus());

        assertTrue(seq2 > seq1);
        assertTrue(seq3 > seq2);
    }

    @Test
    void testHeartbeatUpdate() throws InterruptedException {
        long initialTime = registration.getLastHeartbeat();

        Thread.sleep(50); // Ensure sufficient time difference
        registration.updateHeartbeat();

        // After update, should not be expired with long timeout
        assertFalse(registration.isExpired(60000));

  private val forbiddenLocks = mutableListOf<Any>()

  /** The timestamp of the last taken event, used to measure elapsed time between events. */
  private var lastTimestampNs: Long? = null

  /** Confirm that the thread does not hold a lock on `lock` during the callback. */
  fun forbidLock(lock: Any) {
    forbiddenLocks.add(lock)
  }

  /**

    CRAWLING_EXCEPTION,
    /** Indicates no URL is available in the queue. */
    NO_URL_IN_QUEUE,
    /** Indicates the start of a crawler thread. */
    START_THREAD,
    /** Indicates the finish of a crawler thread. */
    FINISHED_THREAD,
    /** Indicates no response processor is available. */
    NO_RESPONSE_PROCESSOR,
    /** Indicates no rule is available for processing. */
    NO_RULE,

 * invoke methods, they invoke methods on the {@code ForwardingSortedMultiset}.
 *
 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Louis Wasserman
 * @since 15.0
 */
@GwtCompatible
public abstract class ForwardingSortedMultiset<E extends @Nullable Object>

            int expectedSize = buffer.size();

            // Create multiple threads to call size()
            Thread[] threads = new Thread[10];
            for (int i = 0; i < threads.length; i++) {
                threads[i] = new Thread(() -> {
                    for (int j = 0; j < 1000; j++) {
                        assertEquals(expectedSize, buffer.size());
                    }

    failover.handleFailure(channel, error);
    
    // Verify channel marked as failed
    assertEquals(ChannelState.FAILED, channel.getState());
    
    // Verify recovery attempted
    Thread.sleep(2000);
    assertTrue(channel.getState() == ChannelState.ESTABLISHED 
        || manager.getChannels().isEmpty());
}
```

### 7.2 Integration Tests
```java
@Test