@Test
  public void testIsEmpty() {
    CopyOnWriteHashMap empty = newMap();
    CopyOnWriteHashMap map = map5();
    assertTrue(empty.isEmpty());
    assertFalse(map.isEmpty());
  }
isEmpty is true of empty map and false for non-empty
geode-core/src/integrationTest/java/org/apache/geode/internal/util/concurrent/CopyOnWriteHashMapJUnitTest.java