PR #1447 adds new unit tests based on zonemaster/zonemaster#1380.

Four scenarios (GOOD-UNDEL-2, GOOD-UNDEL-3, GOOD-UNDEL-4 and GOOD-UNDEL-11) show inconsistent behavior. When testing with zonemaster-cli all four passes. Reports of that is included in test-zones-output.md in PR zonemaster/zonemaster#1380. When running the unit tests, all four scenarios fail.

The four scenarios have some things in common:

• There is no delegated zone or it cannot be reached.
• There is a working undelegated zone.
• The undelegated zone has out-of-bailiwick name servers.
• The undelegated data is without glue records, but the address records can be looked up.

All other 24 scenarios work as they should, and all scenarios share the same root and hint data.

The issue seen here could be related to the issue reported on the mailing list.