Hello!
I have a code (test) that mocks datetime.datetime.now and the way queryset
filter method works. The code is:
Mock:
@contextlib.contextmanager
def mock_now(dt_value):
"""Context manager for mocking out datetime.now() in unit tests.
Example:
with mock_now(datetime.datetime(2011, 2, 3, 10, 11)):
assert datetime.datetime.now() == datetime.datetime(2011, 2, 3, 10, 11)
Authored by: https://gist.github.com/jimmydo/1113164
"""
class MockDateTime(datetime.datetime):
@classmethod
def now(cls):
# Create a copy of dt_value.
return datetime.datetime(
dt_value.year, dt_value.month, dt_value.day,
dt_value.hour, dt_value.minute, dt_value.second,
dt_value.microsecond,
dt_value.tzinfo
)
real_datetime = datetime.datetime
datetime.datetime = MockDateTime
try:
yield datetime.datetime
finally:
datetime.datetime = real_datetime
Status model like:
class Status(models.Model):
created = models.DateTimeField(_('created'), auto_now_add=True)
timestamp = models.DateTimeField(_('timestamp'), db_index=True)
(...)
And finally code that uses the above:
with mock_now(datetime.datetime(2013, 03, 07, 23, 0, 9)):
period = datetime.timedelta(minutes=24*60)
when = datetime.datetime.now() - period
print 'when: ', repr(when)
stats = Status.objects.filter(timestamp__gt=when)
print 'stats: ', stats
that prints
>>> when: datetime.datetime(2013, 3, 6, 23, 0, 9)
>>> stats: [<Status: 2013-03-06 20:00:09 | 1 | True>, <Status: 2013-03-06
23:30:09 | 1 | False>, <Status: 2013-03-06 23:40:09 | 1 | True>, <Status:
2013-03-07 06:00:09 | 1 | False>, <Status: 2013-03-07 12:00:09 | 1 | True>]
As you see the first Status is 2013-03-06 20:00:09 (it's
status_object.timestamp printed here) that shouldn't be included in results
because 2013-03-06 20:00:09 is less than 2013-03-06 23:00:09
At the same time this works as expected;
with mock_now(datetime.datetime(2013, 03, 07, 23, 0, 9)):
# when isn't calculated here
when = datetime.datetime(2013, 03, 07, 23, 0, 9)
print 'when: ', repr(when)
stats = Status.objects.filter(timestamp__gt=when)
print 'stats: ', stats
printing:
>>> when: MockDateTime(2013, 3, 6, 23, 0, 9)
>>> stats: [<Status: 2013-03-06 23:30:09 | 1 | False>, <Status: 2013-03-06
23:40:09 | 1 | True>, <Status: 2013-03-07 06:00:09 | 1 | False>, <Status:
2013-03-07 12:00:09 | 1 | True>]
when is MockDateTime here and not just datetime.datetime
As well as this works:
# no 'with' here
period = datetime.timedelta(minutes=24*60)
when = datetime.datetime.now() - period
print 'when: ', repr(when)
stats = Status.objects.filter(timestamp__gt=when)
print 'stats: ', stats
printing:
>>> when: datetime.datetime(2013, 3, 6, 23, 0, 9)
>>> stats: [<Status: 2013-03-06 23:30:09 | 1 | False>, <Status: 2013-03-06
23:40:09 | 1 | True>, <Status: 2013-03-07 06:00:09 | 1 | False>, <Status:
2013-03-07 12:00:09 | 1 | True>]
The problem is that the code that I'm going to test does:
when = datetime.datetime.now() - period what causes filter to return
unfiltered results. Any ideas on how to solve that?
Best regards
Jakub
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