The CampaignEvents extension is enabled in several production wikis, including some of the largest. However, the extension isn't gated, which sometimes results in unexpected CI breakage. Over the last 3 weeks, we've had T378780 and r1094455. So, I'm proposing that the extension be added to the gate. The extension's PHPUnit suite runs in 5 seconds locally, and we don't have too many e2e tests, so the impact on build times should be minimal.

The WikimediaCampaignEvents is a small sub-extension with additional Wikimedia-specific features. I'm proposing that we add it to the gate as well, to test the full set of features enabled in production.