Enable parallel unit tests on Debian 12 CI and run Debian 12 server tests on 4 vCPU machine
To use parallel unit tests install python3-pytest-xdist package
and pass --numprocesses=auto option to pytest.
This will only work on Debian 12 because pytest-django gained support for pytest-xdist in version 2.5.0
https://pytest-django.readthedocs.io/en/latest/changelog.html#v2-5-0
Debian 11 ships pytest-django 2.2.0
https://packages.debian.org/bullseye/python3-pytest-xdist
Debian 12 ships pytest-django 3.1.0
https://packages.debian.org/bookworm/python3-pytest-xdist
The dispatcher tests instantly became around 30 seconds faster when run in parallel.
Debian 11 dispatcher test (01:18)
Debian 12 parallel dispatcher test (00:52)
However, the server tests did not get that big of the boost. Debian 12 server tests already slower than Debian 11 by about 60%. Using the parallel test the difference narrowed to around 30%.
Debian 11 server test (01:49)
Debian 12 parallel server test (02:26)
I suspect this is because server tests are more CPU bound and the default runner has 2 vCPUs which are probably 2 SMT threads over 1 core.
I switched to a 4 vCPU machine to Debian 12 server tests and now they are faster than Debian 11 tests.