Using pytest-django and setup takes 7 or 8 minutes?

Question

I am setting up pytest testing for our Django site and it is taking seven or eight (7 or 8) minutes to finish running a single test in which less than a hundred objects are created. This feels like its going to be a massive impediment to developing tests if I can only try five things an hour (given that I will be sure to waste several of those tries on stupid mistakes like typos in filepaths.)

platform win32 -- Python 3.9.1, pytest-6.2.2, py-1.10.0, pluggy-0.13.1 Django 3.1.5

Our site uses django-simple-history (which creates a history counterpart of every table) and django-taggit, and has maybe 25 different apps, of which a couple provide widely reused models (if that matters). Could be 100 or more models all up. My laptop has 8Gb RAM, and an older i7 CPU.

I have set the reusedb option in pytest.ini, but there is no perceptible change. Is this a fixable problem?

This is the code:

import pytest

@pytest.mark.django_db
def test_proj_creation():
    for i in range(5):
        groupname = "G" + str(i)
        group = Group.objects.create(name=groupname)
        username = "U" + str(i)
        user = User.objects.create(username=username)
        user.set_password(username)
        user.groups.set(Group.objects.all())
        proj_name = "P" + str(i)
        project = Project.objects.create(project_name=proj_name)
        project.target_groups.add(group)
        assert user.groups.count() == i+1

When run:

========================================================================================================= test session starts =========================================================================================================
platform win32 -- Python 3.9.1, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
django: settings: mysite6.settings_components.development (from ini)
rootdir: C:\Users\Andrew\AzureKEN\KEN%20development, configfile: pytest.ini
plugins: django-4.1.0
collected 1 item                                                                                                                                                                                                                       

tests\pytest_site.py

And this is where the long pause happens.

Then:

========================================================================================================== warnings summary ===========================================================================================================
tests/pytest_site.py::test_proj_creation
  c:\users\andrew\djdev\lib\site-packages\django\db\models\fields\__init__.py:1367: RuntimeWarning: DateTimeField HistoricalBRVM.last_modified received a naive datetime (1901-01-01 00:00:00) while time zone support is active.
    warnings.warn("DateTimeField %s received a naive datetime (%s)"

-- Docs: https://docs.pytest.org/en/stable/warnings.html
============================================================================================== 1 passed, 1 warning in 695.40s (0:11:35) ===============================================================================================

Answer 1

I'm going to answer my own question - the issue here is that

@pytest.mark.django_db

invokes creation of a blank sqlite database with all the tables created, which is a lot of work. This is configured by running through all the django migrations scripts, and that process requires many minutes. I can reduce this a bit by using the migration "squash" commands to reduce redundancy. The --reuse-db option doesn't seem to work (?) but in any case, we would normally expect to have database changes that would prevent reuse of an existing database.