So I was fixing some slow tests, and whenever I ran them through the pytest command, I was greeted with the dreaded max_locks_per_transaction error.

My first instinct? Just crank up the max_locks_per_transaction from 64 to 1024.

But... that didn’t feel right. I recreate my DB frequently, which means I’d have to set that value again and again. It felt like a hacky workaround rather than a proper solution.

Then, like any developer, I started digging around — first checking the Confluence page for dev docs to see if anyone else had faced this issue. No luck. Then I moved to Slack, and that’s where I found this command someone had shared:

pytest -n=0

This was new to me. So, like any sane dev in 2025, I asked ChatGPT what this was about. That’s how I came across pytest-xdist.

What is pytest-xdist?

The pytest-xdist plugin extends pytest with new test execution modes — the most common one is distributing tests across multiple CPUs to speed up test execution.

What does pytest-xdist do?

Runs tests in parallel using <numprocesses> workers (Python processes), which is a game changer when: – You have a large test suite
– Each test takes a significant amount of time
– Your tests are independent (i.e., no shared global state)

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That’s pretty much it — I plugged in pytest -n=0 and boom, no more transaction locks errors.

Cheers!

References – https://pytest-xdist.readthedocs.io/en/stable/ – https://docs.pytest.org/en/stable/reference/reference.html

#pytest #Python #chatgpt #debugging