public void ToPrice()
        {
            var a = new Accounting()
            {
                Description = "xyz"
            };
            var unitPrice   = new UnitPrice(1, 20, CurrencyUnit.EUR, TimeSpanUnit.Day);
            var measureItem = new TimeSpanItem(2, TimeSpanUnit.Day);
            var ip          = new ItemPrice(unitPrice, measureItem)
            {
                Description = "abc", Accounting = a
            };
            var p = new Price(2, 20, CurrencyUnit.EUR)
            {
                Description = "abc", Accounting = a
            };

            Assert.AreEqual(p, ip.AsPrice());
        }
        public void ToPriceWithCurrencyItem()
        {
            var a = new Accounting()
            {
                Description = "xyz"
            };
            var unitPrice    = new UnitPrice(1, 20, CurrencyUnit.EUR, TimeSpanUnit.Day);
            var measureItem  = new TimeSpanItem(2, TimeSpanUnit.Day);
            var currencyItem = new CurrencyItem(CurrencyUnit.GBP, CurrencyUnit.EUR, 0.9m)
            {
                Stamp = DateTime.Now
            };
            var ip = new ItemPrice(unitPrice, measureItem, currencyItem)
            {
                Description = "abc", Accounting = a
            };
            var p = new Price(1.8m, 20, CurrencyUnit.GBP)
            {
                Description = "abc", Accounting = a
            };

            Assert.AreEqual(p, ip.AsPrice());
        }