Thanks again, @99of9 , for bringing this to light. I tweaked both tests so the expected values are lists, and also the language element in the expected sitelink is a literal (because Z6839 returns literal language elements). With these tweaks the test failures for both of these tests are the same – and they happen because of the inability to construct a matching value for the language element of the expected sitelink. Z6839 returns a literal language element with Z60K1 only, whereas the UI only allows to construct a reference, or a literal element with Z60K1 and Z60K2.

Update – After disconnecting one implementation of Z31988/same Wikidata sitelink and changing the language element of the expected values, in both of these tests, to references, both tests are now passing.

Ideally, one day Z60K2 will be marked as an optional key (Optional keys are discussed frequently and on the roadmap for future work).

Going forward, I think we need a new equality function for Z60 that allows for compared languages to be either reference or literal, and also allows for a missing Z60K2, as proposed in T421468, and that should be used for Z31988/same Wikidata sitelink. We also need for Z6839 to include Z60K2 in the language elements it produces.

Update: because of post-V2-release fixes, both tests are now passing for https://www.wikifunctions.org/view/en/Z31992 ( the implementation of Z31988/same Wikidata sitelink that was disconnected above). However, let's keep this ticket open for the following:

• Update the implementations of https://www.wikifunctions.org/view/en/Z31988 to use the new Z60 built-in equality function for comparing Z6039K2 values.
• Then reconnect https://www.wikifunctions.org/view/en/Z31992.
• Consider updating Z6839 to include Z60K2 in the Z60 instances it produces.