断言错误测试类中的属性和方法

Question

为了练习，我写了一个类BankAccount来学习python中的OOP。为了使我的程序更加冗余，我尝试编写一个测试函数test_BankBankAccount() 来练习如何执行测试函数。

测试函数test_BankBankAccount() 假设测试方法deposit()、withdraw()、transfer() 和get_balance() 是否按预期工作。

但是，测试函数失败了，因为 computed_deposit = test_account.deposit(400)、computed_transfer = test_account.transfer(test_account2, 200) 等内部的方法似乎没有存储我分配给它们的值。

**这是我收到的错误消息（这是我试图避免的确切消息）**

assert success1 and success2 and success3 and success4, (msg1, msg2, msg3, msg4)
AssertionError: ('computet deposit = None is not 400', 'computet transfer = None is not 200', 'computet withdrawal = None is not 200', 'computet balance = 0 is not 0')

这是我迄今为止编写的大部分代码的 sn-p

class BankAccount:
    def __init__(self, first_name, last_name, number, balance):
        self._first_name = first_name
        self._last_name = last_name
        self._number = number
        self._balance = balance

    def deposit(self, amount):
        self._balance += amount

    def withdraw(self, amount):
        self._balance -= amount

    def get_balance(self):
        return self._balance

    def transfer(self,other_account, transfer_amount):
        self.withdraw(transfer_amount)
        other_account.deposit(transfer_amount)                  

    def print_info(self):
        first = self._first_name
        last = self._last_name
        number = self._number
        balance = self._balance

        s = f"{first} {last}, {number}, balance: {balance}"

        print(s)

def main():

    def test_BankBankAccount():
        test_account = BankAccount("Dude", "man", "1234", 0)
        test_account2 = BankAccount("Dude2", "man2","5678", 0)

        expected_deposit = 400
        expected_withdrawal = 200
        expected_transfer = 200
        expected_get_balance = 0

        computed_deposit = test_account.deposit(400)
        computed_transfer = test_account.transfer(test_account2, 200)
        computed_withdrawal = test_account.withdraw(200)
        computed_get_balance = test_account.get_balance()

        #tol = 1E-17

        success1 = abs(expected_deposit == computed_deposit) #< tol
        success2 = abs(expected_transfer == computed_transfer) #< tol
        success3 = abs(expected_withdrawal == computed_withdrawal) #< tol
        success4 = abs(expected_get_balance == computed_get_balance)  #<tol

        msg1 = f"computet deposit = {computed_deposit} is not {expected_deposit}"
        msg2 = f"computet transfer = {computed_transfer} is not {expected_transfer}"
        msg3 = f"computet withdrawal = {computed_withdrawal} is not {expected_withdrawal}"
        msg4 = f"computet balance = {computed_get_balance} is not {expected_get_balance}"
        assert success1 and success2 and success3 and success4, (msg1, msg2, msg3, msg4)

    test_BankBankAccount()

我的问题是：

• 有没有人好心帮我解决这个问题并发现我的错误？

欢迎并感谢所有帮助。

Answer 1

作为 Goodword 答案的替代方案，您可以尝试：

        test_account.deposit(400)
        computed_deposit = test_account.get_balance()
        
        test_account.transfer(test_account2, 200)
        computed_withdrawal = test_account.get_balance()
        computed_transfer = test_account2.get_balance()

        test_account.withdraw(200)
        computed_get_balance = test_account.get_balance()

关于测试，向您致敬！我建议您熟悉 Python 的 unittesting framework，因为从长远来看，它会为您提供良好的服务。

例如，您可以定义一个class 来测试您的BankAccount，例如

import unittest
class TestBankAccount(unittest.TestCase):
    # setUp gets run before every individual test
    def setUp(self):
        self.account1 = BankAccount("First","Account","1234",0)
        self.account2 = BankAccount("Second","Account","5678",200)

    def test_deposit(self):
        self.account1.deposit(400)
        self.assertEqual(self.account1.get_balance(),400)

    def test_withdraw(self):
        self.account2.withdraw(200)
        self.assertEqual(self.account1.get_balance(),0)

    def test_transfer(self):
        self.account2.transfer(self.account1,200)
        self.assertEqual(self.account1.get_balance(),200)
        self.assertEqual(self.account2.get_balance(),0)

if __name__=="__main__":
    unittest.main()
        

Answer 2

问题是您没有从这些成员函数中返回任何内容。

例如，尝试让deposit 看起来像这样：

def deposit(self, amount):
    self._balance += amount
    return self._balance