public void testIsEmpty() {
   setUpTest();
   assertTrue(c.isEmpty());
   HashSet empty = new HashSet();
   c.addComposited(empty);
   assertTrue(c.isEmpty());
   empty.add("a");
   assertTrue(!c.isEmpty());
 }
 public void testClear() {
   setUpTest();
   one.add("1");
   two.add("2");
   c.addComposited(one, two);
   c.clear();
   assertTrue(one.isEmpty());
   assertTrue(two.isEmpty());
   assertTrue(c.isEmpty());
 }