}
        },
        directExecutor());
    list.execute();
    assertEquals(1, runCalled.get());
    list.execute();
    assertEquals(1, runCalled.get());
  }

  public void testExecute_idempotentConcurrently() throws InterruptedException {
    CountDownLatch okayToRun = new CountDownLatch(1);
    AtomicInteger runCalled = new AtomicInteger();
    list.add(
        new Runnable() {
          @Override