EventLogging on https://test2.wikipedia.org is currently configured to not use meta.wikimedia.org as its Schema source, but instead to use itself own local schema source. In theory, that would be useful for testing purposes of some kind.

However, in practice, I have not seen this happen. If anything, it actually causes log noise:

2018-06-03T14:20:20	INFO	EventLogging	mw1324	test2wiki	Request to https://test2.wikipedia.org/w/api.php?action=jsonschema&revid=17799034&formatversion=2 failed.
2018-06-03T14:20:20	INFO	EventLogging	mw1324	test2wiki	Request to https://test2.wikipedia.org/w/api.php?action=jsonschema&revid=17799034&formatversion=2 failed.
2018-06-03T14:18:03	INFO	EventLogging	mw1327	test2wiki	Request to https://test2.wikipedia.org/w/api.php?action=jsonschema&revid=17799034&formatversion=2 failed.

As well as client-side in the browser:

(error) [NavigationTiming] Missing or empty schema

This is because various extensions are enabled on test2wiki that use EventLogging.

At first I thought, it just meant that the schemas aren't defined locally (but that they could be), but thats not the case. Even if I were to create a Schema by the same name, it still wouldn't work because it's keyed by revision ID, which (to a first approximation) cannot be created at-will.

For some repository-client relationships (such as CentralNotice and Wikibase), I think using test2wiki in this way makes sense. But I think we should reconsider whether this is useful for EventLogging.

Alternatively, if we believe that it is useful, we should find a way to disable stuff that is coded against Meta-Wiki (not sure how, though).

For the purposes of debugging or testing, I'm not sure what a user can actually test, given it would still require server-side patching to consume or register a schema module. That could be done via mwdebug live hacks, but at that point, it would seem much easier to do in the Beta Cluster, or locally.

For use cases of UI testing, the production site (meta.wikimedia.org) and Beta Cluster both seem adequate already.

See also:

• T51723: EventLogging on the beta cluster should work well and match production (tracking)
• rOMWC81e77c0752c5: Set $wgEventLoggingDBname on test2wiki to test2wiki