@Test
	public void testRetainAll() {
		strings.add("Three");
		strings.add("Four");
		List<String> retain = Arrays.asList("Three", "Four");
		assertTrue("Testing retainAll", strings.retainAll(retain));
		assertFalse("Testing retainAll", strings.retainAll(retain));
		String[] expected = {"Three", "Three","Four"};
		assertArrayEquals("Testing retain result",expected, strings.toArray());
	}