*/
  @SuppressWarnings({"InlineLambdaConstant", "UnnecessaryLambda"})
  private static final Runnable EMPTY_RUNNABLE = () -> {};

  /** Returns a {@link Runnable} instance that does nothing when run. */
  public static Runnable doNothing() {
    return EMPTY_RUNNABLE;
  }

  private Runnables() {}

      }
    }

    private static class RunnableExecutorPair {
      final Runnable runnable;
      final Executor executor;

      RunnableExecutorPair(Runnable runnable, Executor executor) {
        this.runnable = runnable;
        this.executor = executor;
      }

      void execute() {
        try {
          executor.execute(runnable);
        } catch (RuntimeException e) {

import org.jspecify.annotations.NullUnmarked;

/**
 * Unit tests for {@link Runnables}.
 *
 * @author Olivier Pernet
 */
@GwtCompatible
@NullUnmarked
public class RunnablesTest extends TestCase {
  public void testDoNothingRunnableIsSingleton() {
    assertThat(Runnables.doNothing()).isSameInstanceAs(Runnables.doNothing());
  }

      if (!executed) {
        runnables = new RunnableExecutorPair(runnable, executor, runnables);
        return;
      }
    }
    // Execute the runnable immediately. Because of scheduling this may end up getting called before
    // some of the previously added runnables, but we're OK with that. If we want to change the
    // contract to guarantee ordering among runnables we'd have to modify the logic here to allow
    // it.

      }
    }

    private static class RunnableExecutorPair {
      final Runnable runnable;
      final Executor executor;

      RunnableExecutorPair(Runnable runnable, Executor executor) {
        this.runnable = runnable;
        this.executor = executor;
      }

      void execute() {
        try {
          executor.execute(runnable);
        } catch (RuntimeException e) {

import org.jspecify.annotations.NullUnmarked;

/**
 * Unit tests for {@link Runnables}.
 *
 * @author Olivier Pernet
 */
@GwtCompatible
@NullUnmarked
public class RunnablesTest extends TestCase {
  public void testDoNothingRunnableIsSingleton() {
    assertThat(Runnables.doNothing()).isSameInstanceAs(Runnables.doNothing());
  }

    list.add(new MockRunnable(countDownLatch), exec);
    list.add(new MockRunnable(countDownLatch), exec);
    assertEquals(3L, countDownLatch.getCount());

    list.execute();

    // Verify that all of the runnables execute in a reasonable amount of time.
    assertTrue(countDownLatch.await(1L, SECONDS));
  }

  public void testExecute_idempotent() {
    AtomicInteger runCalled = new AtomicInteger();

    list.add(new MockRunnable(countDownLatch), exec);
    list.add(new MockRunnable(countDownLatch), exec);
    assertEquals(3L, countDownLatch.getCount());

    list.execute();

    // Verify that all of the runnables execute in a reasonable amount of time.
    assertTrue(countDownLatch.await(1L, SECONDS));
  }

  public void testExecute_idempotent() {
    AtomicInteger runCalled = new AtomicInteger();

      "FINE: Q10000 scheduled after 100 µs: task",
      "FINE: Q10000 starting              : task",
      "FINE: Q10000 finished run in   0 µs: task",
    )
  }

  /** Inspect how many runnables have been enqueued. If none then we're truly sequential. */
  @Test fun singleQueueIsSerial() {
    redQueue.execute("task one", 100.µs) {
      log += "one:run@${taskFaker.nanoTime} parallel=${taskFaker.isParallel}"
    }

   * otherwise-concurrent GC cycle.
   */
  private static final class TaskNonReentrantExecutor extends AtomicReference<RunningState>
      implements Executor, Runnable {

    /**
     * Used to update and read the latestTaskQueue field. Set to null once the runnable has been run
     * or queued.
     */
    @Nullable ExecutionSequencer sequencer;

    /**