没有失败的测试，就不能写生产代码

先写代码后写测试？删除它。从头开始。

# Good: 清晰名称，测试真实行为，一件事
def test_retries_failed_operations_3_times():
    attempts = 0
    def operation():
        nonlocal attempts
        attempts += 1
        if attempts < 3:
            raise Exception('fail')
        return 'success'
    
    result = retry_operation(operation)
    assert result == 'success'
    assert attempts == 3

❌ Bad: 模糊名称，测试 mock 而不是真实代码
def test_retry_works():
    mock = MagicMock()
    mock.side_effect = [Exception(), Exception(), 'success']

pytest tests/path/test_name.py -v
# 或项目对应的测试命令

# Good: 刚好够通过测试
def retry_operation(fn, max_retries=3):
    for i in range(max_retries):
        try:
            return fn()
        except Exception as e:
            if i == max_retries - 1:
                raise e

❌ Bad: 过度设计，加入了测试没要求的功能
def retry_operation(fn, options={max_retries=3, backoff='linear', onRetry=...})
    # YAGNI - 你不需要这个

pytest tests/path/test_name.py -v

def test_rejects_empty_email():
    result = submit_form({'email': ''})
    assert result['error'] == 'Email required'

$ pytest
FAIL: expected 'Email required', got undefined

def submit_form(data):
    if not data.get('email', '').strip():
        return {'error': 'Email required'}
    # ...

$ pytest
PASS