The LinkSuggest2 extension has a sub repo Caret.js, which is not known by the test framework and such this gives error when test are running:
19:55:21 There was 1 failure:
19:55:21
19:55:21 1) ResourcesTest::testFileExistence with data set #553 ('/srv/jenkins-workspace/worksp...ret.js', 'ext.LinkSuggest2', 'modules/vendor/Caret.js/src/j...ret.js')
19:55:21 File 'modules/vendor/Caret.js/src/jquery.caret.js' referenced by 'ext.LinkSuggest2' must exist.
19:55:21 Failed asserting that file "/srv/jenkins-workspace/workspace/mwext-testextension-php55/src/extensions/LinkSuggest2/modules/vendor/Caret.js/src/jquery.caret.js" exists.
19:55:21
19:55:21 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/tests/phpunit/structure/ResourcesTest.php:23
19:55:21 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/tests/phpunit/MediaWikiTestCase.php:400
19:55:21 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/maintenance/doMaintenance.php:111One solution is to bundle the files with the extension, makes install easier. See T154806 for a discussion about this problem on another repo