Faster parallel pytest-django

We at Buser recently migrated from Django unittests to pytest. It is amazing how much you can improve your tests with pytest.

Unfortunately our CI/CD was really slow after this change.

I discovered parallel pytest-django do their setup different than Django unittests. Django create a template database and copy it to every test node, pytest-django create one database per node. Running this setup with migrations took more than 2 minutes just to have the database created.

This is a problem mostly for CI/CD, because local you can run with --reuse-db and the overhead is minimal, only when you have database migrations.

I wanted to fix this in pytest-django, but I discovered it is difficult because pytest-xdist don't have a global setup and teardown.

Now I have a small hack, working great so far. This is the script running our tests:

./ shell -c "
from django.test.utils import setup_databases
from xdist.plugin import pytest_xdist_auto_num_workers
setup_databases(verbosity=True, interactive=False, parallel=pytest_xdist_auto_num_workers())
pytest --reuse-db -n auto

Django unittests generate names like test_yourdb_1, test_yourdb_2 and pytest-django generate names like test_yourdb_gw0, test_yourdb_gw1, their names don't match, I had to make a fixture to monkey patch their behaviors.

from pytest_django.fixtures import _set_suffix_to_test_databases
from pytest_django.lazy_django import skip_if_no_django

# Original code:
def django_db_modify_db_settings_xdist_suffix(request):

    xdist_suffix = getattr(request.config, "workerinput", {}).get("workerid")
    if xdist_suffix:
        # 'gw0' -> '1', 'gw1' -> '2', ...
        suffix = str(int(xdist_suffix.replace('gw', '')) + 1)

I tried to make a pull request to pytest-django, but this issue exists because pytest-xdist don't have hooks to run before and after every node.

Comments !