#28361: One of the tutorial test cases fail on certain systems
-----------------------------------------+-------------------------------
Reporter: marton bognar | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: 1.11
Severity: Normal | Keywords: datetime test
Triage Stage: Unreviewed | Has patch: 1
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
-----------------------------------------+-------------------------------
On my Windows machine the test
`test_was_published_recently_with_old_question` fails. I'm fairly sure I
copied every piece of code correctly, but even on a theoretical level I'm
not sure why it would succeed.
{{{
>python manage.py test polls
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
......F.
======================================================================
FAIL: test_was_published_recently_with_old_question
(polls.tests.QuestionModelTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "[...]\polls\tests.py", line 81
, in test_was_published_recently_with_old_question
self.assertIs(old_question.was_published_recently(), False)
AssertionError: True is not False
----------------------------------------------------------------------
Ran 8 tests in 0.031s
FAILED (failures=1)
Destroying test database for alias 'default'...
}}}
The test case in question:
{{{
time = timezone.now() - datetime.timedelta(days=1)
old_question = Question(pub_date=time)
self.assertIs(old_question.was_published_recently(), False)
}}}
The check used in the function is `now - datetime.timedelta(days=1) <=
self.pub_date <= now`, and the test sets the `pub_date` to exactly one day
before now. Can we be sure that time passes between creating the `time`
variable and checking it against the question's `pub_date`? This certainly
doesn't seem to be the case on my machine (hence the fail).
I think a good and unambiguous solution would be to set `time` to 1 day
and 1 second in the past. This still test the edge case, but it is
guaranteed that the check will succeed, even with `<=`.
I'm not quite sure what the difference is, but an interesting comparison
is how python handles the following on this machine:
{{{
>>> datetime.now(), datetime.now(), datetime.now(), datetime.now(),
datetime.now(), datetime.now()
(datetime.datetime(2017, 7, 4, 17, 28, 20, 132149),
datetime.datetime(2017, 7, 4, 17, 28, 20, 132149), datetime.datetime(2017,
7, 4, 17, 28, 20, 132149), datetime.datetime(2017, 7, 4, 17, 28, 20,
132149), datetime.datetime(2017, 7, 4, 17, 28, 20, 132149),
datetime.datetime(2017, 7, 4, 17, 28, 20, 132149))
}}}
Whereas on my Linux machine every instance has a different value.
System specs:
Windows 8.1 (Version 6.3, Build 9600)
Python 3.6.1
Django 1.11.3
--
Ticket URL: <https://code.djangoproject.com/ticket/28361>
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