final ConcurrentMap<String, Integer> delegate = new ConcurrentHashMap<>();

    @Override
    protected ConcurrentMap<String, Integer> delegate() {
      return delegate;
    }
  }

  public void testPutIfAbsent() {
    TestMap map = new TestMap();
    map.put("foo", 1);
    assertEquals(Integer.valueOf(1), map.putIfAbsent("foo", 2));
    assertEquals(Integer.valueOf(1), map.get("foo"));
    assertNull(map.putIfAbsent("bar", 3));

    assertTrue(map.containsKey("2"));
    assertTrue(map.containsKey("3"));
    assertEquals(1L, map.get("1"));
    assertEquals(2L, map.get("2"));
    assertEquals(3L, map.get("3"));
  }

  public void testPutIfAbsent() {
    AtomicLongMap<String> map = AtomicLongMap.create();
    String key = "key";
    long newValue = random.nextInt(MAX_ADDEND);
    for (int i = 0; i < ITERATIONS; i++) {
      long before = map.get(key);