public void Add_Negative()
        {
            var storage = new FundStorage(Money.Dollar(123));

            Assert.Throws <ArgumentException>(() => storage.Add(Money.Dollar(-20)));
        }
        public void Initial()
        {
            var storage = new FundStorage(Money.Dollar(123));

            Assert.Equal(Money.Dollar(123), storage.Funds);
        }
 public void Initial_Fail()
 {
     Assert.Throws <ArgumentException>(() => new FundStorage(Money.Dollar(-123)));
 }