+1 Andréas
One of my projects runs (currently) 1,248 tests using SQLite3 in 72
minutes on my local Windows 10 dev laptop. That laptop has both a SSD
and a hard disk. Foolishly I opted to use the SSD for software
installations and the hard disk for development and thus the tests. I
was concerned that overexercising the SSD might wear it out. I've since
been advised that I shouldn't worry so one of these days I'll reorganise
things and maybe see that 72 minutes drop somewhat.
However, those same tests take 285 minutes on a headless PC running
Ubuntu 16.04 LTS server with Postgres 9.6
There are only one or two tests which generate slightly different error
messages between SQLite3 and Postgres and that is trivial to manage.
Most tests are database heavy, requiring queries and calling/testing
model methods.
Consequently, I use - and recommend - SQLite for dev tests and Postgres
for deployment testing.
Cheers
Mike
On 15/09/2018 1:45 AM, Andréas Kühne wrote:
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
<mailto: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.
fromdjango.test import TestCase, testcases
class OurTestCase(TestCase):
reset_sequences =True def _fixture_setup(self):
for db_namein 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
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