of the NOTICE file are for informational purposes only and
          do not modify the License. You may add Your own attribution
          notices within Derivative Works that You distribute, alongside
          or as an addendum to the NOTICE text from the Work, provided
          that such additional attribution notices cannot be construed
          as modifying the License.

      You may add Your own copyright statement to Your modifications and

    String key = "key";
    long addend = random.nextInt(MAX_ADDEND);
    for (int i = 0; i < ITERATIONS; i++) {
      long before = map.get(key);
      long result = map.addAndGet(key, addend);
      long after = map.get(key);
      assertEquals(before + addend, after);
      assertEquals(after, result);
      addend = after;
    }
    assertEquals(1, map.size());

    String key = "key";
    long addend = random.nextInt(MAX_ADDEND);
    for (int i = 0; i < ITERATIONS; i++) {
      long before = map.get(key);
      long result = map.addAndGet(key, addend);
      long after = map.get(key);
      assertEquals(before + addend, after);
      assertEquals(after, result);
      addend = after;
    }
    assertEquals(1, map.size());