Currently, "Only main test build and SonarQube" are shown, but sometimes a +2 is given without tests, and any failures to those tests are not added to the test results display
Examples: patches by libup that are self +2'ed, eg https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CognitiveProcessDesigner/+/642215
(for reference, not sure what the display is actually called, but I'm referring to the table of test results shown as a result of work at T206453 and T256575)
I don't have much opinion on which test results to include. @Krinkle suggested on https://gerrit.wikimedia.org/r/c/operations/puppet/+/609519/2/modules/gerrit/files/homedir/review_site/static/gerrit-theme.html#277 to limit to only "Main test build succeeded" comments, which led to omitting the results of the other tests.
The relevant commit in our puppet repo is d25fbce4e900ffeb2ece66b5c5735dbbd6c7ad2e
Once there is an agreement on which results to show, that commit can be reverted or adapted.
The "Gate pipeline build" is a superset of "Main test build" and only appears after the C+2 event. I think it's a good idea indeed to include that instead of "Main test build", when present. Displaying both would likely lead to confusion especially if the outcomes were different. Whichever one is commented latest, supersedes any earlier sets (not combined).