【跟着AI学Python】Python进阶:测试驱动开发(TDD)

pip install pytest pytest-cov

bank_system/├── bank.py                 # 账户逻辑├── test_bank.py            # 测试文件（命名以 test_ 开头）└── data/    └── accounts.jsonl      # 账户数据文件

# test_bank.pyimport pytestfrom bank import BankAccount, SavingsAccount, CheckingAccount, InsufficientFundsError, InvalidAmountErrorclass TestBankAccount:    """基类账户测试"""    def test_deposit_valid_amount(self):        """测试有效存款"""        account = SavingsAccount("Alice")        account.deposit(100)        assert account.balance == 100.0    def test_deposit_invalid_amount(self):        """测试无效存款（负数）"""        account = SavingsAccount("Alice")        with pytest.raises(InvalidAmountError):            account.deposit(-50)    def test_account_id_unique(self):        """测试账号唯一性"""        acc1 = SavingsAccount("A")        acc2 = CheckingAccount("B")        assert acc1.account_id != acc2.account_idclass TestSavingsAccount:    """储蓄账户测试"""    def setup_method(self):        """每个测试前初始化"""        self.account = SavingsAccount("Alice")        self.account.deposit(1000)  # 初始余额 1000    def test_withdraw_success(self):        """成功取款（含手续费）"""        self.account.withdraw(100)        # 100 + 1 手续费 = 101 扣除        assert self.account.balance == 899.0    def test_withdraw_insufficient_funds(self):        """余额不足取款"""        with pytest.raises(InsufficientFundsError):            self.account.withdraw(2000)  # 2000 + 1 > 1000    def test_withdraw_invalid_amount(self):        """无效取款金额"""        with pytest.raises(InvalidAmountError):            self.account.withdraw(0)class TestCheckingAccount:    """支票账户测试"""    def test_overdraft_allowed(self):        """允许透支到 -500"""        account = CheckingAccount("Bob")        account.deposit(300)        account.withdraw(700)  # 300 - 700 = -400 > -500        assert account.balance == -400.0    def test_overdraft_exceeded(self):        """透支超限"""        account = CheckingAccount("Bob")        with pytest.raises(InsufficientFundsError):            account.withdraw(600)  # 0 - 600 = -600 < -500

# test_bank.py（新增）from unittest.mock import mock_open, patchfrom bank import save_accountsdef test_save_accounts():    """测试保存账户（使用 Mock 避免真实文件操作）"""    # 创建模拟账户    account = SavingsAccount("Test")    account.account_id = 999    account._balance = 500.0    # Mock open() 函数    with patch("builtins.open", mock_open()) as mock_file:        save_accounts([account])        # 验证 open 被调用        mock_file.assert_called_once_with("data/accounts.jsonl", "w", encoding="utf-8")        # 验证写入内容        handle = mock_file()        written_content = "".join(call[0][0] for call in handle.write.call_args_list)        assert '"owner": "Test"' in written_content        assert '"balance": 500.0' in written_content

def test_load_accounts_file_not_found():    """测试文件不存在时的行为"""    with patch("bank.os.path.exists", return_value=False):        accounts = list(load_accounts())  # 应返回空        assert len(accounts) == 0

pytest  # 自动发现 test_*.py

pytest --cov=bank --cov-report=html --cov-report=term

# bank.py（在 BankAccount 类中添加）def transfer_to(self, target_account: "BankAccount", amount: float) -> bool:    """    转账到目标账户    :param target_account: 收款账户    :param amount: 转账金额    :return: 是否成功    """    if amount <= 0:        raise InvalidAmountError(amount, "转账金额必须为正数")    if self is target_account:        raise BankError("不能转账给自己")    # 执行取款（会自动扣除手续费）    if not self.withdraw(amount):        return False    # 执行存款    target_account.deposit(amount)    # 记录日志    logger.info(        f"💰 转账成功 | 从账号: {self.account_id} | "        f"到账号: {target_account.account_id} | 金额: {amount:.2f}"    )    return True

# test_bank.pydef test_transfer_between_accounts():    """测试账户间转账"""    alice = SavingsAccount("Alice")    bob = SavingsAccount("Bob")    alice.deposit(500)    alice.transfer_to(bob, 200)  # ← 功能尚未实现！    assert alice.balance == 299.0  # 500 - 200 - 1(手续费)    assert bob.balance == 200.0

AttributeError: 'SavingsAccount' object has no attribute 'transfer_to'

# bank.pyclass BankAccount(ABC):    # ...    def transfer_to(self, target_account, amount):        """转账到目标账户"""        if not isinstance(target_account, BankAccount):            raise ValueError("目标必须是 BankAccount 实例")        self.withdraw(amount)        target_account.deposit(amount)