Hi,
Just my 5 cents. I think you are doing the tests wrong. I don't believe
that doing testing against hard coded values is at all correct - and it
isn't actually that hard to change the tests to a simpler way. The values
of the PK's aren't really necessary for your test to be true either - how
does that translate to a real use case? You should probably check for A
value in the pk field, but not a specific value, because that doesn't
result in any added value for your customer?
Also changing the way django runs tests feels like working against the
framework rather than with it? I would probably much prefer changing the
tests than changing the way the framework runs my tests.... Another issue
you may face is if Django changes the underlying code, then you will get
strange failures as well...
I don't think that 70 tests is that much to change either - we work with a
project that could fail a considerable amount of tests during a refactor -
and then we need to fix them. The same goes here I think - you did a change
to the infrastructure that made the tests invalid - rewrite the tests :-)
Best regards,
Andréas
Den fre 14 sep. 2018 kl 17:32 skrev Hezi Halpert <chez...@gmail.com>:
> I would like to share with you an issue we encounter while moving from
> sqlite to postgres with heavily use of Django testing.
>
> We have Django app with ~700 tests. Most of them accessing database. We
> recently migrated the database from sqlite to postgres.
> Many of our tests were written in a way that compares actual pk’s
> (hard-coded pks or just file/json comparisons) . Since Django testing on
> sqlite (testcases.TestCase class) creates in-memory database (which is
> being reseted every unit test by default), we never had a problem with it.
> However, Django TestCase on postgres create completely another test db
> which preserves the pk sequences between different tests. And since many of
> our tests were written in a way that compares actual pk’s they all start
> fail - depends on the exact tests execution order.
> Even tests which expect some pk and are were not failed yet, can
> potentially failed in the future - depends on adding/editing other tests
> which may change the db sequence
>
> We consider the following solutions:
>
> 1. Move to TransactionTestCase (instead of TestCase) and use
> “reset_sequences = True” flag. Cons: TransactionTestCase reduces
> performance dramatically (~4 times longer in some of the tests)
> 2. Refactor all failed tests: remove all hard-coded references to the
> pk. Cons: Require much Dev effort (we had more then 70 such tests)
> 3. Route the database in settings.py such it will use sqlite instead
> of postgres when running tests. Cons: It will not actually test the real
> scenarios - not an option
> 4. Combine reset_sequences flag with TestCase in our own version to
> TestCase: OurTestCase class and make everything to inherit from it. This is
> the option we finally decided of. See below.
>
>
> from django.test import TestCase, testcases
>
>
> class OurTestCase(TestCase):
> reset_sequences = True
>
> def _fixture_setup(self):
> for db_name in self._databases_names(include_mirrors=False):
> if self.reset_sequences:
> self._reset_sequences(db_name)
> if self.fixtures:
> call_command('loaddata', *self.fixtures, **{'verbosity': 0,
> 'database': db_name})
> if not testcases.connections_support_transactions():
> self.setUpTestData()
> return super(TestCase, self)._fixture_setup()
> self.atomics = self._enter_atomics()
>
>
> Another problem of these kind of tests is the default ordering assumption
> of Django which changes significantly between postgres and sqlite when
> testing.
> Therefore, models included in such tests must have a hint for Django
> regarding the default ordering retrieval.
> Our solution was to make all models inherit from DexterModelDefaultOrder
> (below)
>
>
> class DexterModelDefaultOrder(models.Model):
> class Meta:
> abstract = True
> ordering = ['id']
>
>
>
> I hope it (will) help someone
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to django-users+unsubscr...@googlegroups.com.
> To post to this group, send email to django-users@googlegroups.com.
> Visit this group at https://groups.google.com/group/django-users.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/django-users/ffcd3cc9-c3be-44ba-9665-a4ded5fed492%40googlegroups.com
> <https://groups.google.com/d/msgid/django-users/ffcd3cc9-c3be-44ba-9665-a4ded5fed492%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
> For more options, visit https://groups.google.com/d/optout.
>
--
You received this message because you are subscribed to the Google Groups
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/CAK4qSCeeyDaUnTb95uO_LpdkLknS-V6tWtm8q3%2BY58FgEs_AnQ%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.
