@Test
public void testRemove() {

   ConcurrentLongHashMap<String> map = new ConcurrentLongHashMap<>();
   assertTrue(map.isEmpty());
   assertNull(map.put(1, "one"));
   assertFalse(map.isEmpty());
   assertFalse(map.remove(0, "zero"));
   assertFalse(map.remove(1, "uno"));
   assertFalse(map.isEmpty());
   assertTrue(map.remove(1, "one"));
   assertTrue(map.isEmpty());
}