Changing settings.TIME_ZONE at runtime

[dbrgn]

With this test file:

import pytest
from django.utils.timezone import get_current_timezone

def test_europe(settings):
    settings.TIME_ZONE = 'UTC'
    assert settings.TIME_ZONE == 'UTC'
    tz = get_current_timezone()
    assert tz.__class__.__name__ == 'UTC'

def test_america(settings):
    settings.TIME_ZONE = 'America/Lima'
    assert settings.TIME_ZONE == 'America/Lima'
    tz = get_current_timezone()
    assert tz.__class__.__name__ == 'America/Lima'

The first test succeeds, but the second test isn't able to change the timezone.

tests/test_utils.py .F

======================================================== FAILURES ========================================================
______________________________________________________ test_america ______________________________________________________
tests/test_utils.py:15: in test_america
>       assert tz.__class__.__name__ == 'America/Lima'
E       assert 'UTC' == 'America/Lima'
E         - UTC
E         + America/Lima
===================================== 1 failed, 1 passed, 1 skipped in 0.11 seconds ======================================

Same problem if I use the setattr workaround mentioned at #46 (comment).

Is this a scoping problem?

[dbrgn]

Even if the tests are in separate files, they fail.

[pelme]

Not all settings can be changed during run time, and those that can cannot always be changed in a reliable way.

Changing the default timezone looks problematic: get_current_timezone() calls get_default_timezone() to get the default timezone when it is needed, and the default timezone is then cached (in _localtime: https://github.com/django/django/blob/master/django/utils/timezone.py#L166). Which means, that get_default_timezone() will always return the same thing for the life time of the Python process.

In this case, you are probably looking for django.utils.timezone.override or django.utils.timezone.activate to change the current Django timezone at run time.

Closing this issue now, since this is a design flaw/feature in Django and not in pytest-django.

[dbrgn]

Thanks! In that case it should probably be documented in the fixtures.settings docs.

[pelme]

It might be sufficient to point to this warning in Django's docs:
https://docs.djangoproject.com/en/dev/topics/testing/tools/#django.test.override_settings