The files in this part of the tree are not browser tests; they're documents intended for testing the behavior of conformance checkers (e.g., validator.nu and the W3C Nu Markup Validator).
To update the generated tests, run wpt update-built --include conformance-checkers.
TK: We should have here some details about the contents of the existing subdirectories in this tree...
Curious committers should see the makefile.