RdfBuilderTest contains tests dealing with non-local entities. At least some of these tests are useful for the structured data for Commons functionality, but a lot of it still uses the unused repository prefixes in entity IDs in the test data.
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/929366/2 "blindly" removes some of the prefixes to unblock shipping the patch that disallows repository prefixes in entity IDs, but there are still a lot of other tests and fixture files that should be cleaned up. This work could benefit from someone who knows their way around these RdfBuilder tests to help with the cleanup.