Omitting TestMessages.md (updated by script with each release), I can see four places with references to Basic04 that were missed: README.md, ImplementedTestCases.md, MessageTagSpecification.md and IssueLabels.md.

I am aware of those and have decided not to include them.

README.md -- Updated by script at release time. See https://github.com/zonemaster/zonemaster/blob/master/docs/specifications/tests/README.md?plain=1#L70

ImplementedTestCases.md -- Updated by script at release time. See https://github.com/zonemaster/zonemaster/blob/master/docs/specifications/tests/ImplementedTestCases.md?plain=1#L1

MessageTagSpecification.md -- Just an example, not a reference. Can be updated when the file is updated for other reasons.

IssueLabels.md -- Not a direct reference. Relevant to be updated, but in a separate PR when we do more updates to the file.

Implemented in zonemaster/zonemaster-engine#1143