* deterministic.
 *
 * This class ensures that at most one thread is running at a time. This is initially the JUnit test
 * thread, which yields its execution privilege while calling [runTasks], [runNextTask], or
 * [advanceUntil]. These functions don't return until the task threads are all idle.
 *
 * Task threads release their execution privilege in these ways:
 *

    start();
  }

  // Thread.stop() is okay because all threads started by a test are dying at the end of the test,
  // so there is no object state put at risk by stopping the threads abruptly. In some cases a test
  // may put a thread into an uninterruptible operation intentionally, so there is no other way to
  // clean up these threads.
  @SuppressWarnings("deprecation")
  @Override

        // Test thread safety with concurrent operations
        final int threadCount = 10;
        Thread[] threads = new Thread[threadCount];
        final boolean[] results = new boolean[threadCount];

        for (int i = 0; i < threadCount; i++) {
            final int index = i;
            threads[i] = new Thread(() -> {
                String thumbnailId = "concurrent-" + index;

                }
            });
        }

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

        // Wait for all threads to complete
        for (Thread thread : threads) {
            thread.join(5000); // 5 second timeout
        }

        // Verify no errors occurred during concurrent execution
        assertFalse(hasError.get());

            });
        }

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

        // Wait for all threads to complete
        for (Thread thread : threads) {
            try {
                thread.join();
            } catch (InterruptedException e) {
                fail("Thread interrupted");
            }
        }

            }

            // 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

                });
                threads[i].start();
            }

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

        // Then
        for (int i = 0; i < threadCount; i++) {
            assertTrue(results[i], "Thread " + i + " should have completed successfully");
        }
    }

                } catch (Exception e) {
                    logger.error("Thread {} failed", index, e);
                    results[index] = false;
                }
            });
            threads[i].start();
        }

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

        // Then

        // Simulate concurrent failures
        Thread[] threads = new Thread[5];
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(() -> failover.handleFailure(failedChannel, error));
            threads[i].start();
        }

        // Wait for all threads to complete
        for (Thread thread : threads) {
            thread.join(1000);
        }

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

            // Wait for all threads to complete
            for (Thread thread : threads) {
                try {
                    thread.join();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    fail("Thread interrupted");