@Test
  public void customerSummary() {
    Bank bank = new Bank();
    Customer john = new Customer("John");
    john.openAccount(new Account(Account.CHECKING));
    bank.addCustomer(john);

    assertEquals("Customer Summary\n - John (1 account)", bank.customerSummary());
  }
  @Test
  public void maxi_savings_account() {
    Bank bank = new Bank();
    Account checkingAccount = new Account(Account.MAXI_SAVINGS);
    bank.addCustomer(new Customer("Bill").openAccount(checkingAccount));

    checkingAccount.deposit(3000.0);

    assertEquals(170.0, bank.totalInterestPaid(), DOUBLE_DELTA);
  }
  @Test
  public void checkingAccount() {
    Bank bank = new Bank();
    Account checkingAccount = new Account(Account.CHECKING);
    Customer bill = new Customer("Bill").openAccount(checkingAccount);
    bank.addCustomer(bill);

    checkingAccount.deposit(100.0);

    assertEquals(0.1, bank.totalInterestPaid(), DOUBLE_DELTA);
  }