Add tests to registry_spec

[timgrein]

Add some missing tests to registry_spec.rb to have more coverage.

Checklists

Pre-Review Checklist

• [x] Covered the changes with automated tests
• [x] Tested the changes locally

[github-actions[bot]]

💔 Failed to create backport PR(s)

The backport operation could not be completed due to the following error: There are no branches to backport to. Aborting.

The backport PRs will be merged automatically after passing CI.

To backport manually run: backport --pr 441 --autoMerge --autoMergeMethod squash