Why shouldn't tests be run on a production server?

From semantic-mediawiki.org

Is it just because of performance concerns? Because then you can still run them when setting up the wiki.

20:28, 15 March 2019

It is an established practice that you run tests (unit or integration) not on a production cluster unless you have a specific task you'd like to verify.

Aside from the mentioned best practice, tests try not to leak any setup information (meaning any data required for the tests) into a test/production database by cloning all tables into a different namespace (prefix) but it may happen (happened in the past as we rely on MW's `CloneDatabase` but I haven't seen it happen as of late).

03:30, 16 March 2019