After T210758: Add browser test for preview functionality to MediaWiki core we want to make sure the core browser tests are run every time before we merge a patch in the Two-Column-Edit-Conflict-Merge extension. It should ideally be run as part of the "Gate pipeline build" that runs a single time after a patch received a Code-Review+2, but before it is merged.
As far as I'm aware of the setup for this is in https://gerrit.wikimedia.org/r/#/admin/projects/integration/config.
Note this job must run with the corresponding feature enabled! In this particular case, either the user running the test must have the option twocolconflict set to 1 to enable the BetaFeatures, or $wgTwoColConflictBetaFeature = false must be set to have the feature enabled by default.
When we figured out how to run this job, we plan to apply the same to all other codebases we are working on now and in the future (most notably Move-Files-To-Commons).