@Test
public void testRemove() {

   ConcurrentLongHashSet set = new ConcurrentLongHashSet();
   assertTrue(set.isEmpty());
   assertTrue(set.add(1));
   assertFalse(set.isEmpty());
   assertFalse(set.remove(0));
   assertFalse(set.isEmpty());
   assertTrue(set.remove(1));
   assertTrue(set.isEmpty());
}