@Test
 public void invalidCreditTest() {
   assertEquals(bank.getCredit("Rubber"), null);
 }
 @Test
 public void validCreditTest() {
   bank.setCredit("Gold", Double.valueOf(2.0));
   assertEquals(bank.getCredit("Gold"), Double.valueOf(2.0));
 }
 @Test
 public void invalidAssignmentTest() {
   assertEquals(bank.getAssignment("gish"), null);
 }
 @Test
 public void invalidRomanFromStringTest() {
   bank.setAssignment("pish", "I");
   assertEquals(bank.getRomanFromString("pish gish"), "");
 }
 @Test
 public void validAssignmentTest() {
   bank.setAssignment("pish", "I");
   assertEquals(bank.getAssignment("pish"), "I");
 }