### Question:
ListOps { static <T> List<T> append(List<T> list1, List<T> list2) { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } private  ListOps();   }### Answer:
@Test public void testAppendingEmptyLists() { assertEquals( Collections.emptyList(), ListOps.append(Collections.emptyList(), Collections.emptyList()) ); }
@Ignore("Remove to run test") @Test public void testAppendingListToEmptyList() { assertEquals( Arrays.asList('1', '2', '3', '4'), ListOps.append(Collections.emptyList(), Arrays.asList('1', '2', '3', '4')) ); }
@Ignore("Remove to run test") @Test public void testAppendingNonEmptyLists() { assertEquals( Arrays.asList("1", "2", "2", "3", "4", "5"), ListOps.append(Arrays.asList("1", "2"), Arrays.asList("2", "3", "4", "5")) ); }