@Test
 public void testEmpty() throws Exception {
   subject.add("cows");
   subject.add("sheep");
   subject.add("ducks");
   subject.add("mice");
   subject.add("dogs");
   subject.add("cats");
   subject.add("birds");
   subject.clear();
   boolean nothing = subject.isEmpty();
   Assert.assertTrue(nothing);
   subject.add("birds");
   nothing = subject.isEmpty();
   Assert.assertFalse(nothing);
 }
 @Test
 public void testClear() throws Exception {
   subject.add("cows");
   subject.add("sheep");
   subject.add("ducks");
   subject.add("mice");
   subject.add("dogs");
   subject.add("cats");
   subject.add("birds");
   subject.clear();
   int size = subject.size();
   Assert.assertEquals(0, size);
   subject.add("birds");
   size = subject.size();
   Assert.assertEquals(1, size);
 }