The generate of code coverage for mediawiki/core takes way too long (more than 3 hours) and eventually reach the 5 hours time limit (parent task T232706).
PHPUnit has support for phpdbg which is dramatically faster. An example for a single test:
xdebug
php tests/phpunit/phpunit.php tests//phpunit/includes/api/ApiQuerySiteinfoTest.php --filter testContinuation --coverage-html /tmp/mwcover-xdebug Time: 45.86 seconds, Memory: 68.50MB
phpdbg (with Xdebug disabled)
phpdbg -qrr tests/phpunit/phpunit.php tests//phpunit/includes/api/ApiQuerySiteinfoTest.php --filter testContinuation --coverage-html /tmp/mwcover-phpdbg Time: 7.62 seconds, Memory: 74.50MB
We should thus have CI to switch to phpdbg (and make sure Xdebug is disabled).
Some infos: