});
        }

        for (Thread th : threads) {
            th.start();
        }
        for (Thread th : threads) {
            th.join();
        }
        assertEquals(num, count.get());
        assertEquals(num, valueSet.size());

        Set<String> valueSet2 = Collections.synchronizedSet(new HashSet<>());
        threads = new Thread[threadNum];

    void testConcurrentAccess() throws InterruptedException {
        // Test thread safety of getInstance
        LogStream.setInstance(testStream);

        final LogStream[] instances = new LogStream[10];
        Thread[] threads = new Thread[10];

        for (int i = 0; i < threads.length; i++) {
            final int index = i;
            threads[i] = new Thread(() -> {
                instances[index] = LogStream.getInstance();

  }

  /**
   * Add a shutdown hook to wait for thread completion in the given {@link ExecutorService service}.
   * This is useful if the given service uses daemon threads, and we want to keep the JVM from
   * exiting immediately on shutdown, instead giving these daemon threads a chance to terminate
   * normally.
   *
   * @param service ExecutorService which uses daemon threads

    }

    @Test
    public void testThreadSafety() throws InterruptedException {
        // Test concurrent updates from multiple threads
        Thread[] threads = new Thread[10];

        for (int i = 0; i < threads.length; i++) {
            final int index = i;
            threads[i] = new Thread(() -> {
                for (int j = 0; j < 100; j++) {
                    String name = "file" + index + "_" + j + ".txt";

        // When - Multiple threads accessing trees concurrently
        for (int t = 0; t < threadCount; t++) {
            final int threadId = t;
            executor.submit(() -> {
                try {
                    startLatch.await(); // Wait for all threads to be ready

                    for (int i = 0; i < opsPerThread; i++) {

            });
        }

        // Start all threads simultaneously
        for (Thread thread : threads) {
            thread.start();
        }

        // Wait for all threads to complete
        for (Thread thread : threads) {
            thread.join();
        }

        // All threads should see the initialized state
        for (boolean result : initResults) {

   * intentionally, so there is no other way to clean up these threads. (The better solution,
   * though, would be to run the tests that use TestThread in separate VMs so that their threads
   * don't hang around during other tests.)
   */
  @Override
  public void tearDown() throws Exception {
    try {
      Thread.class.getMethod("stop").invoke(this);
      join();

   * intentionally, so there is no other way to clean up these threads. (The better solution,
   * though, would be to run the tests that use TestThread in separate VMs so that their threads
   * don't hang around during other tests.)
   */
  @Override
  public void tearDown() throws Exception {
    try {
      Thread.class.getMethod("stop").invoke(this);
      join();

            }

            // When
            for (Thread thread : threads) {
                thread.start();
            }
            for (Thread thread : threads) {
                thread.join();
            }

            // Then
            for (int i = 0; i < threadCount; i++) {
                assertTrue(success[i], "Thread " + i + " failed");
            }
        }

        @Test

                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                } finally {
                    endLatch.countDown();
                }
            });
        }

        startLatch.countDown(); // Start all threads
        assertTrue(endLatch.await(30, TimeUnit.SECONDS), "All threads should complete within timeout");
        executor.shutdown();