public void SalesItemTaxDecoratorTaxTest()
        {
            SalesItemTaxDecorator taxDecorator = new SalesItemTaxDecorator(new SalesItemStub(10M, 0M), new TaxStub(0.1M));

            decimal tax = taxDecorator.GetSalesTax();

            Assert.AreEqual(1M, tax);
        }