def test_mixed_addition():
five_dollars = Currency(5, "USD")
ten_euro = Currency(10, "EUR")
bank = Bank()
bank.addRate("EUR", "USD", 2)
result = bank.reduce(five_dollars.plus(ten_euro), "USD")
assert result == Currency(10, "USD")
def testPlusReturnsSum():
five = Currency(5, "USD")
one = Currency(1, "USD")
result = five.plus(one)
assert result.augend == five
assert result.addend == one
