@Test
 public void invisibleCardsAreNotShown() {
   aceOfHearts.setVisible(false);
   hand.addCard(aceOfHearts);
   String UNKNOW_CARD = "**";
   assertEquals(UNKNOW_CARD, hand.toString());
 }
 @Test
 public void testFlippedCardDoesNotCountOnValue() {
   aceOfHearts.setVisible(false);
   hand.addCard(aceOfHearts);
   final int VALUE_OF_HAND_WITH_FLIPPED_CARDS = 0;
   assertEquals(VALUE_OF_HAND_WITH_FLIPPED_CARDS, hand.getValue());
 }
 @Test
 public void testFlipCardsLeaveCardsAsVisible() {
   aceOfHearts.setVisible(false);
   hand.addCard(aceOfHearts);
   hand.flipCards();
   String ACE_OF_HEARTS_REPRESENTATION = "AH";
   assertEquals(ACE_OF_HEARTS_REPRESENTATION, hand.toString());
 }