public void TestDepositNegativeAmount()
        {
            Deposit deposit = null;

            try
            {
                decimal amount = -100;
                deposit = new Deposit(amount);
            }
            finally
            {
                Assert.IsNull(deposit);

            }
        }
        public void TestAmount()
        {
            Deposit deposit = new Deposit((Decimal)100.11);

            Assert.AreEqual((Decimal)100.11, deposit.GetValue());
        }