引发异常，如果脚本失败 [英] Raise exception if script fails

问题描述

我有一个python脚本，tutorial.py。我想从一个文件test_tutorial.py，这是我的Python测试套件中运行此脚本。如果tutorial.py执行没有任何异常，我想测试通过;如有异常tutorial.py的执行过程中引发的，我想测试失败。

I have a python script, tutorial.py. I want to run this script from a file test_tutorial.py, which is within my python test suite. If tutorial.py executes without any exceptions, I want the test to pass; if any exceptions are raised during execution of tutorial.py, I want the test to fail.

下面是我在写test_tutorial.py，这确实的不可以产生所需的行为：

Here is how I am writing test_tutorial.py, which does not produce the desired behavior:

from os import system
test_passes = False
try:
    system("python tutorial.py")
    test_passes = True
except:
    pass
assert test_passes

我觉得上面的控制流不正确：如果tutorial.py抛出一个异常，那么断言线永远不会执行。

I find that the above control flow is incorrect: if tutorial.py raises an exception, then the assert line never executes.

什么是测试如果外部脚本会引发异常的正确方法？

What is the correct way to test if an external script raises an exception?

推荐答案

如果没有错误取值将 0 ：

from os import system
s=system("python tutorial.py")
assert  s == 0

或者使用子：

from subprocess import PIPE,Popen

s = Popen(["python" ,"tutorial.py"],stderr=PIPE)

_,err = s.communicate() # err  will be empty string if the program runs ok
assert not err

您的try /除正赶上从教程文件没有，你可以将它移出一切，它会表现得一样的：

Your try/except is catching nothing from the tutorial file, you can move everything outside the it and it will behave the same:

from os import system
test_passes = False

s = system("python tutorial.py")
test_passes = True

assert test_passes

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