Without the slightest sense of irony, I actually strongly suspect such a test suite would only be valid at one moment in time, since the timezone legislation is almost continuously in flux. That's why <https://www.iana.org/time-zones> and its friend <https://www.oracle.com/java/technologies/javase/tzupdater-re...> exist. As if to illustrate my point, the latest update was 2025-03-22, presumably nuking any such conformance test from Mar 21st
In that case, you'd have unit tests that confirm behaviors like compatibility or failure of some operations between types and integrations tests which pull an up to date DB of rules and tests against that.
It would have to take the real world into account, no? Additionally it could test various timezone definition permutations without necessarily being dependent on a real one.