public void TestCaseThree()
        {
            MasterCard person1MasterCard1 = new MasterCard(100m);
            MasterCard person1MasterCard2 = new MasterCard(100m);

            WalletType person1Wallet = new WalletType();

            person1Wallet.AddCard(person1MasterCard1)
            .AddCard(person1MasterCard2);

            WalletPerson person1 = new WalletPerson();

            person1.AddWallet(person1Wallet);

            MasterCard person2MasterCard = new MasterCard(100m);
            Visa       person2Visa       = new Visa(100m);

            WalletType person2Wallet = new WalletType();

            person2Wallet.AddCard(person2MasterCard)
            .AddCard(person2Visa);

            WalletPerson person2 = new WalletPerson();

            person2.AddWallet(person2Wallet);

            Assert.Equal(10m, person1.CalculateTotalInterest());
            Assert.Equal(10m, person1Wallet.CalculateTotalInterest());
            Assert.Equal(15m, person2.CalculateTotalInterest());
            Assert.Equal(15m, person2Wallet.CalculateTotalInterest());
        }
        public void TestCaseTwo()
        {
            Discover   discover   = new Discover(100m);
            MasterCard masterCard = new MasterCard(100m);
            Visa       visa       = new Visa(100m);

            WalletType wallet1 = new WalletType();

            wallet1.AddCard(discover)
            .AddCard(visa);

            WalletType wallet2 = new WalletType();

            wallet2.AddCard(masterCard);

            Assert.Equal(11m, wallet1.CalculateTotalInterest());
            Assert.Equal(5m, wallet2.CalculateTotalInterest());
        }