@Test
 public void confirmingOrderEmptiesCart() throws Exception {
   testee.addBookToCart(2);
   testee.confirmOrder();
   assertEquals(0, testee.getCart().getBookCount());
   assertEquals(
       asList(testee.findBookById(2)), testee.getCheckout().getConfirmedOrder().getBooks());
 }
 @Test
 public void addBookToCart() throws Exception {
   testee.addBookToCart(1);
   assertEquals(1, testee.getCart().getBookCount());
   assertEquals(asList(testee.findBookById(1)), testee.getCart().getBooks());
 }