Historically, we've used nose as the test runner, with a custom test

runner script responsible for setting up a test run.
Unfortunately, nose 1.x hasn't been updated in a long while, and isn't

compatible with modern versions of Python 3. The forks also don't

support Python 3 very well. nose2 does, but is so different that it's

not a great option for us.
Instead, we're moving to pytest. This is a much more modern test

runner with a lot of interesting capabilities and a wide ecosystem of

plugins.
We now use this and define what little test setup we still need in

conftest.py, which is where we can define hooks for pytest to load.
We also use the pytest-django module, which is an official pytest

plugin for setting up a Django environment.
Developers can now run pytest directly to run the test suite. The old

./tests/runtests.py still works, but is deprecated, and merely wraps

pytests anyway.
Note that we still have a test runner we ship with Django that uses

nose. For now, this will continue to use nose, but we won't be using

it. We will need to evaluate a modernization or deprecation plan for

this.

Unit tests pass for all supported versions of Python.