arc_patterns_python_ch01_valueObjects2.py

fiver = Money('gbp', 5)
tenner = Money('gbp', 10)

def can_add_money_values_for_the_same_currency():
    assert fiver + fiver == tenner

def can_subtract_money_values():
    assert tenner - fiver == fiver

def adding_different_currencies_fails():
    with pytest.raises(ValueError):
        Money('usd', 10) + Money('gbp', 10)

def can_multiply_money_by_a_number():
    assert fiver * 5 == Money('gbp', 25)

def multiplying_two_money_values_is_an_error():
    with pytest.raises(TypeError):
        tenner * fiver