Mostly covered, but a number of recent failures
See also T252076
Current coverage can be found at https://doc.wikimedia.org/cover/mediawiki-core/includes/Revision/index.html
Specific classes with low coverage:
RenderedRevision - 46.15% of functions and methods
RevisionRenderer - 33.33% of functions and methods
RevisionStore - 51.47% of functions and methods