2.11. 测试调试

2.11.1. 在单元测试中测试异常情况

import unittest

def parse_int(s):
    return int(s)

class TestConversion(unittest.TestCase):
    def test_bad_int(self):
        self.assertRaises(ValueError, parse_int, 'N/A')


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

2.11.2. 将测试输出用日志记录到文件中

import sys
import unittest

def main(out=sys.stderr, verbosity=2):
    loader = unittest.TestLoader()
    suite = loader.loadTestsFromModule(sys.modules[__name__])
    unittest.TextTestRunner(out,verbosity=verbosity).run(suite)

if __name__ == '__main__':
    with open('testing.out', 'w') as f:
        main(f)

2.11.3. 忽略或期望测试失败

import unittest
import os
import platform

class Tests(unittest.TestCase):
    @unittest.skip('skipped test')
    def test_1(self):
        self.fail('should have failed!')

    @unittest.skipIf(os.name=='posix', 'Not supported on Unix')
    def test_2(self):
        import winreg

    @unittest.skipUnless(platform.system() == 'Darwin', 'Mac specific test')
    def test_3(self):
        self.assertTrue(True)

    @unittest.expectedFailure
    def test_4(self):
        self.assertEqual(2+2, 5)

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

2.11.4. 处理多个异常

try:
   f = open(filename)
except (FileNotFoundError, PermissionError):
   pass



try:
   f = open(filename)
except OSError:
   pass

2.11.5. 捕获所有异常

try:
   ...
except Exception as e:
   ...
   log('Reason:', e)       # Important!

2.11.6. 创建自定义异常

需要继承 Exception

2.11.7. 捕获异常后抛出另外的异常

try:
   ...
except SomeException as e:
   raise DifferentException() from e

2.11.8. 重新抛出被捕获的异常

try:
   ...
except SomeException as e:
   raise

2.11.9. 输出警告信息

import warnings

def func(x, y, logfile=None, debug=False):
   if logfile is not None:
         warnings.warn('logfile argument deprecated', DeprecationWarning)
   ...

2.11.10. 调试基本的程序崩溃错误

1. print

2. pdb

3. traceback.print_stack()