How do I freeze time and assert on a timestamp in a template?

Question

p1/urls.py:

from django.urls import path
from . import views
urlpatterns = [
    path('t1/', views.t1),
]

p1/views.py:

from django.shortcuts import render
def t1(request):
    return render(request, 'p1/t1.html')

p1/templates/p1/t1.html:

<?xml version="1.0" encoding="UTF-8"?>
<root timestamp="{% now 'Y-m-d H:i:s' %}">...</root>

p1/settings.py:

TIME_ZONE = 'Asia/Tokyo'
USE_TZ = True
INSTALLED_APPS = [
    ...
    'p1',
]

p1/tests.py:

from django.test import TestCase
from freezegun import freeze_time

class MyTestCase(TestCase):
    @freeze_time('2019-01-02 03:04:05')
    def test_freezegun(self):
        expected_response = '''
            <?xml version="1.0" encoding="UTF-8"?>
            <root timestamp="2019-01-02 03:04:05">...</root>
        '''
        response = self.client.get('/t1/')
        self.assertXMLEqual(expected_response, response.content.decode(response.charset))

Then,

$ ./manage.py test
Creating test database for alias 'default'...
F
======================================================================
FAIL: test_freezegun (p1.tests.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/yuri/_/1/env/lib/python3.7/site-packages/freezegun/api.py", line 658, in wrapper
    result = func(*args, **kwargs)
  File "/home/yuri/_/1/p1/p1/tests.py", line 12, in test_freezegun
    self.assertXMLEqual(expected_response, response.content.decode('utf-8'))
  File "/home/yuri/_/1/env/lib/python3.7/site-packages/django/test/testcases.py", line 854, in assertXMLEqual
    self.fail(self._formatMessage(msg, standardMsg))
AssertionError: '\n            <?xml version="1.0" encoding="UTF-8"?>\n            <root timesta [truncated]... != '<?xml version="1.0" encoding="UTF-8"?>\n<root timestamp="2019-01-02 12:04:05">. [truncated]...
- 
-             <?xml version="1.0" encoding="UTF-8"?>
? ------------

+ <?xml version="1.0" encoding="UTF-8"?>
-             <root timestamp="2019-01-02 03:04:05">...</root>
? ------------                            ^^

+ <root timestamp="2019-01-02 12:04:05">...</root>
?                             ^^

-         

----------------------------------------------------------------------
Ran 1 test in 0.031s

FAILED (failures=1)
Destroying test database for alias 'default'...
System check identified no issues (0 silenced).

What am I doing wrong? Adding tz_offset to freeze_time doesn't help.

Did you tried checking utc, datetime, django now, values in shell ? I think timezone offset should work. — Umair Mohammad, May 22 '19 at 12:01
adding `tz_offset` to `freeze_time` should work, what do you mean by "doesn't help"? — dirkgroten, May 22 '19 at 13:16
I only remember that both expected and actual times kept changing as I changed `tz_offset`. Probably I had a wrong idea of how this all is going to work. — x-yuri, May 25 '19 at 12:28

score 2 · Accepted Answer · answered May 25 '19 at 12:22

The thing here is that most of the time Django stores timestamps in UTC. And converts to local time only when presenting data to the user. So, the time I pass to freeze_time is treated as UTC, but then now in the template converts it to local time. As such, I've got to either specify local time in expected_response (2019-01-02 12:04:05), or time zone in "freeze time" string (2019-01-02 03:04:05 JST), or add tz_offset (JST is UTC+9h, so tz_offset=-9).

How do I freeze time and assert on a timestamp in a template?

1 Answers1