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From: Peter Otten <__peter__@web.de>
Subject: Re: Is this a good way to implement testing
Date: Sun, 03 May 2015 10:45:29 +0200
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Xref: csiph.com comp.lang.python:89837

Cecil Westerhof wrote:

> Another question. Is it acceptable to have it in the module itself, or
> should I put it in something like test_<module>.py? The code for
> testing is bigger as the code for the implementation, so I am leaning
> to putting it in a separate file.

Definitely use an established testing framework instead of rolling your own, 
and definitely put it into a separate file -- by the time there is good 
coverage the test code is usually much bigger than the tested code.

Be aware that there is also doctest which scans docstrings for text 
resembling interactive Python sessions. Doctests are both tests and usage 
examples, so I think it's good to put a few of these into the module. Here's 
how it works:

$ cat factorial.py
def factorial(n):
    """Calculate the factorial 1 * 2 * ... * n.

    >>> factorial(0)
    1
    >>> factorial(1)
    1
    >>> factorial(10)
    3628800
    """
    return 1
$ python3 -m doctest factorial.py
**********************************************************************
File "/home/peter/clpy/factorial.py", line 8, in factorial.factorial
Failed example:
    factorial(10)
Expected:
    3628800
Got:
    1
**********************************************************************
1 items had failures:
   1 of   3 in factorial.factorial
***Test Failed*** 1 failures.
$