@Test(timeout = 200)
 public void testPut() {
   addBasic();
   assertEquals("First element is incorrect", new Integer(0), list.first());
   assertEquals("Last element is incorrect", new Integer(10), list.last());
   assertEquals("Size of the list is incorrect", 11, list.size());
 }
 // This is an example of how your SkipList is tested
 // for efficiency.
 @Test(timeout = 200)
 public void testPutSingle() {
   list.put(1);
   assertEquals(1, list.size());
   assertEquals(new Integer(1), list.first());
   assertEquals(new Integer(1), list.last());
   assertEquals(2, randomness.getNumFlips());
 }
 @Test(timeout = 200)
 public void testEmptyBasic() {
   assertNull(list.first());
   assertNull(list.last());
   assertNull(list.get(1));
   assertNull(list.remove(1));
   assertEquals(
       "Empty set not being returned for an empty list", list.dataSet(), new HashSet<Integer>());
 }
 @Test(timeout = 1000)
 public void testNullLast() {
   assertNull(list.last());
 }