On 04/25/2017 10:15 PM, INADA Naoki wrote:
This is one examples I merged "untested line of code".
https://github.com/python/cpython/pull/162/files#diff-0ad86c44e7866421ecaa5ad2c0edb0e2R552
+ file_object = builtins.open(f, 'wb')
+ try:
+ self.initfp(file_object)
+ except:
+ file_object.close()
+ raise
`self.initfp()` is very unlikely raise exceptions. But MemoryError,
KeyboardInterrupt or
other rare exceptions may be happen.
Test didn't cover this except clause. But I merged it because:
* this code is simple enough.
* I can write test for it with mocking `self.initfp()` to raise
exception. But such test code
have significant maintenance cost. I don't think this except clause
is important enough
to maintain such code.
I'm curious as to the maintenance cost -- surely it's write once, forget until you have to change that method again?
How often are we changing that method?
If I remove the except clause, all lines are tested, but there is
(very unlikely)
leaking unclosed file. Which are "broken"?
Definitely the (unlikely) leaking of a file, possibly the untested closing of
an otherwise leaked file.
Coverage is very nice information to find code which should be tested,
but not tested.
But I don't think "all code should be tested".
All code should be tested. Doesn't mean we can, but that should be the goal.
It may make hard to improve Python.
Adding missing tests _is_ improving Python.
--
~Ethan~
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