public void DepositMoney()
        {
            BankTeller teller  = new BankTeller(db);
            double     money   = 100;
            double     balance = teller.CheckBalance(5);

            teller.DepositMoney(money, 5);
            double newBalance = teller.CheckBalance(5);

            Assert.Equal(money + balance, newBalance);
        }