Pytest下的Python测试运行没有正确捕获CalledProcessError异常

Question

当运行 Python 在 Pytest (py.test) 中进行 doctests 时，我现在正面临一个奇怪的行为。以下片段突出显示了行为。

当通过 python2.7 ./weirdpytestbehaviour_test.py.

会通过

通过 py.test ./weirdpytestbehaviour_test.py --doctest-modules --tb=short.

未通过

如果我将语句 except CalledProcessError as e: 更改为 except Exception as e: 那么 doctests 也会通过 py.test.

似乎 py.test 对 CalledProcessError 异常类型有一些特殊处理。代码在 py.test 中执行时采用不同的评估路径，这是非常不直观的。我如何控制或调整该行为？

#!/usr/bin/python
# coding=utf-8
# file: 'weirdpytestbehaviour_test.py'
from subprocess import check_output, CalledProcessError

def func(success):
    """The worker function.

    >>> func(success=True)
    >>> func(success=False)
    Ouch!
    Special treatment of this particular failure...
    """
    try:
        # Now invoke a subprocess
        if success:
            # Will always succeed and return with an exit code of 0
            check_output('echo "Hello!"; exit 0', shell=True)
        else:
            # Will always succeed and return with an exit code of 1
            check_output('echo "Ouch!"; exit 1', shell=True)

    # Does not catch the exception under pytest
    # 'except Exception as e:' would work as expected
    except CalledProcessError as e:
        print(e.output),
        if "Ouch!" in e.output:
            print("Special treatment of this particular failure...")
        else:
            raise

if __name__ == '__main__':
    import doctest
    doctest.testmod()

失败情况下py.test的输出（试图捕获上面的CalledProcessError）如下：

$ py.test ./weirdpytestbehaviour_test.py --doctest-modules --tb=short 
Test session starts (platform: linux2, Python 2.7.6, pytest 3.4.2, pytest-sugar 0.9.1)
[...]

007 The worker function.
008 
009     >>> func(success=True)
010 
011     >>> func(success=False)
UNEXPECTED EXCEPTION: CalledProcessError()
Traceback (most recent call last):

  File "/usr/lib/python2.7/doctest.py", line 1315, in __run
    compileflags, 1) in test.globs

  File "<doctest experiments.weirdpytestbehaviour_test.func[1]>", line 1, in <module>

  File "weirdpytestbehaviour_test.py", line 22, in func
    check_output('echo "Ouch!"; exit 1', shell=True)

  File "/usr/lib/python2.7/subprocess.py", line 573, in check_output
    raise CalledProcessError(retcode, cmd, output=output)

CalledProcessError: Command 'echo "Ouch!"; exit 1' returned non-zero exit status 1

weirdpytestbehaviour_test.py:11: UnexpectedException

weirdpytestbehaviour_test.py ⨯                                                                                                                                                                                        100% ██████████

Results (0.19s):
       1 failed
         - weirdpytestbehaviour_test.py:11 [doctest] weirdpytestbehaviour_test.func

Answer 1

经过反复试验，我通过卸载解决了这个问题，re-installing 不仅是 pytest，还有我使用的插件。之后它又开始工作了。

清理缓存（__pycache__）没有效果。显然pytest及其插件的安装有问题。

Pytest下的Python测试运行没有正确捕获CalledProcessError异常

Python test run under Pytest does not catch CalledProcessError exceptions correctly

python

doctest

subprocess

exception

pytest