在Pytest下運行的Python測試無法正確捕獲CalledProcessError異常

Question

我目前在Pytest（ py.test ）中運行Python doctests時遇到一種奇怪的行為。 以下代碼片段突出顯示了該行為。

• 當通過python2.7 ./weirdpytestbehaviour_test.py調用腳本時，doctest 確實通過了。
• 通過py.test ./weirdpytestbehaviour_test.py --doctest-modules --tb=short調用腳本時，doctest 不會通過 。
• 如果我將except CalledProcessError as e:的語句except CalledProcessError as e: except Exception as e:更改except Exception as e:則將doctests除外，然后還將py.test傳遞。

似乎py.test對CalledProcessError異常類型有一些特殊處理。 在py.test執行時，代碼采用不同的評估路徑是非常不直觀的。 如何控制或調整該行為？

#!/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()

失敗情況下py.test的輸出（嘗試捕獲上述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

經過一番嘗試和錯誤之后，我不僅卸載並重新安裝了pytest，還卸載並重新安裝了我使用的插件，從而解決了此問題。 之后，它又開始工作了。

清理緩存（ __pycache__ ）無效。 顯然pytest及其插件的安裝有問題。