@Test
  public void testKeySetToArray() {
    CustomEntryConcurrentHashMap map = map5();
    Set s = map.keySet();
    Object[] ar = s.toArray();
    assertTrue(s.containsAll(Arrays.asList(ar)));
    assertEquals(5, ar.length);
    ar[0] = m10;
    assertFalse(s.containsAll(Arrays.asList(ar)));
  }
keySet.toArray returns contains all keys
geode-core/src/integrationTest/java/org/apache/geode/internal/util/concurrent/cm/ConcurrentHashMapJUnitTest.java