@Test
public void testMap() throws Exception {
    final ExecutorService executor = Executors.newFixedThreadPool(32);

    final ConcurrentMap<String, String> map = new NonBlockingHashMap<>();
    final String key = UUID.randomUUID().toString();

    final int numberOfIterations = 10_000;
    final CountDownLatch latch = new CountDownLatch(numberOfIterations);

    CopyOnWriteArrayList<String> addedList = new CopyOnWriteArrayList<>();
    CopyOnWriteArrayList<String> removedList = new CopyOnWriteArrayList<>();

    for (int i = 0; i < numberOfIterations; i++) {
        if (i % 2 == 0) {
            executor.submit(() -> {
                String added = UUID.randomUUID().toString();
                map.put(key, added);

                addedList.add(added);

                latch.countDown();
            });
        } else {
            executor.submit(() -> {
                String removed = map.remove(key);

                if (removed != null) {
                    removedList.add(removed);
                }

                latch.countDown();
            });
        }
    }

    assertTrue(latch.await(5, TimeUnit.SECONDS));

    assertEquals(addedList.size(), Sets.newHashSet(addedList).size());
    assertEquals(removedList.size(), Sets.newHashSet(removedList).size());
}