第17章：Python TDD回顾与总结钱币类开辟 - ToB企服应用市场:ToB评测及商务社交产业平台

import unittest
class Bank:
def __init__(self):
self.rates = {}
def addRate(self, from_currency, to_currency, rate):
self.rates[(from_currency, to_currency)] = rate
def rate(self, from_currency, to_currency):
if from_currency == to_currency:
return 1
return self.rates.get((from_currency, to_currency), 1)
def reduce(self, source, to):
if isinstance(source, Sum):
amount = source.augend.reduce(self, to).amount + source.addend.reduce(self, to).amount
return Money(amount, to)
elif isinstance(source, Money):
rate = self.rate(source.currency, to)
return Money(source.amount / rate, to)
class Expression:
def reduce(self, bank, to):
pass
class Money(Expression):
def __init__(self, amount, currency):
self.amount = amount
self.currency = currency
def plus(self, addend):
return Sum(self, addend)
def times(self, multiplier):
return Money(self.amount * multiplier, self.currency)
def reduce(self, bank, to):
rate = self.rate(bank, to)
return Money(self.amount / rate, to)
class Sum(Expression):
def __init__(self, augend, addend):
self.augend = augend
self.addend = addend
def reduce(self, bank, to):
amount = self.augend.reduce(bank, to).amount + self.addend.reduce(bank, to).amount
return Money(amount, to)
class Dollar(Money):
def __init__(self, amount):
super().__init__(amount, "USD")
class Franc(Money):
def __init__(self, amount):
super().__init__(amount, "CHF")
class TestAllCurrencyOperations(unittest.TestCase):
def test_mixed_addition(self):
bank = Bank()
bank.addRate("CHF", "USD", 2)
five_dollars = Dollar(5)
ten_francs = Franc(10)
result = five_dollars.plus(ten_francs).reduce(bank, "USD")
self.assertEqual(result.amount, 10)
self.assertEqual(result.currency, "USD")
def test_dollar_multiplication(self):
five_dollars = Dollar(5)
result = five_dollars.times(3)
self.assertEqual(result.amount, 15)
self.assertEqual(result.currency, "USD")
if __name__ == '__main__':
unittest.main()

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class Dollar:
def __init__(self, amount):
self.amount = amount
def times(self, multiplier):
return 0 # 伪实现，仅为使测试通过

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def test_dollar_multiplication():
five = Dollar(5)
result = five.times(2)
assert result == 10

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def test_dollar_multiplication():
five = Dollar(5)
result = five.times(2)
assert result == 10
result = five.times(3) assert result == 15 ten = Dollar(10) result = ten.times(4) assert result == 40

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class Dollar:
def __init__(self, amount):
self.amount = amount
def times(self, multiplier):
return self.amount * multiplier

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