private void verifyContents(Collection<? extends Object> contents, Bag<? extends Object> cl) {
		Set<Object> set = new HashSet<Object>(contents); 
		
		cl.reset();
		for (cl.reset(); cl.hasNext(); ) {
			Object obj = cl.next();
			assertTrue(set.contains(obj));
			set.remove(obj);
		}
		assertTrue(set.isEmpty());
	}