Tests don't seem to support ES2025

[marekdedic]

I tried to add support for ES private class elements in #1287, but unfortunately, it seems that the test suite doesn't support ES2025.

Repro: In #1287 , revert 92c1e7b and run tests.

[ota-meshi]

I fixed some issues with CI 👍 #1290
I've been busy lately, so I'll check other PRs next week or so.