@Test
 public void multipleRows() {
   assertEquals(87, model.getRowCount());
   assertEquals(START_YEAR, model.getValueAt(0, 0));
   assertEquals(BEGINNING_BALANCE, model.getValueAt(0, 1));
   assertEquals(new Dollar(11000), model.getValueAt(1, 1));
   assertEquals(END_YEAR, model.getValueAt(86, 0));
 }
 @Test
 public void oneRow() {
   assertEquals(START_YEAR, model.getValueAt(0, 0));
   assertEquals(BEGINNING_BALANCE, model.getValueAt(0, 1));
   assertEquals(BEGINNING_PRINCIPAL, model.getValueAt(0, 2));
   assertEquals(new Dollar(0), model.getValueAt(0, 3));
   assertEquals(new Dollar(1000), model.getValueAt(0, 4));
   assertEquals(new Dollar(11000), model.getValueAt(0, 5));
 }