@Test(expected = InvalidValueException.class)
 public void testCantAddNegativeChocolateToInventroy() throws Exception {
   CM.addChocolateInventory(-1);
 }
 @Test(expected = InvalidValueException.class)
 public void testCantAddMoreThanLimitChocolateToInventroy() throws Exception {
   assertEquals(20, CM.checkChocolateInventory());
   CM.addChocolateInventory(81);
 }