The MediaWiki core tests HtmlFormatterTest::testTransform.testTransform and TidyTest::testTidyWrapping.testTidyWrapping do not pass with HHVM. They die with:
Unable to load internal tidy class. [Called from MWTidy::internalClean in includes/parser/MWTidy.php at line 250]
The HHVM version used is the latest from apt.wikimedia.org:
HipHop VM 3.3.1 (rel) Compiler: heads/master-0-gaab439ff2621541ec1a197976ec698be1a8bf1be Repo schema: ef03a9ff7249bca56eabd688c45d47e836e9d387 Extension API: 20140829
And the configuration from https://gerrit.wikimedia.org/r/#/c/178806/
Example Jenkins run: https://integration.wikimedia.org/ci/job/mediawiki-phpunit-hhvm/3/testReport/