Seen in this build which is trying to fix T418774: Wikibase CI broken: Call to undefined method WikibaseLibraryTestCase::suite():
There were 15 errors:
1) MobileFrontendHooksTest::testOnBeforePageDisplay with data set #0 (true, true, true, true, true, array('a'), 1, 'mf-m=a', false)
RuntimeException: Database backend disabled
/workspace/src/includes/libs/Rdbms/LoadBalancer/LoadBalancerDisabled.php:57
/workspace/src/includes/Page/LinkCache.php:450
/workspace/src/includes/Page/LinkCache.php:489
/workspace/src/includes/Page/PageStore.php:186
/workspace/src/includes/Page/PageStore.php:153
/workspace/src/includes/Page/PageStore.php:325
/workspace/src/includes/Title/Title.php:3725
/workspace/src/includes/Title/Title.php:1069
/workspace/src/includes/Title/Title.php:1088
/workspace/src/extensions/ParserMigration/src/Oracle.php:155
/workspace/src/extensions/ParserMigration/src/Oracle.php:42
/workspace/src/extensions/MobileFrontend/includes/MobileFrontendHooks.php:1142
/workspace/src/extensions/MobileFrontend/includes/MobileFrontendHooks.php:912
/workspace/src/extensions/MobileFrontend/tests/phpunit/integration/MobileFrontendHooksTest.php:140
[several copies of this failure…]
14) MobileFrontendHooksTest::testArticleParserOptions with data set "mobile, parsoid, special namespace" (true, true, -1, false)
InvalidArgumentException: WikiPage constructed on a Title that cannot exist as a page: Special:Test
/workspace/src/includes/Page/WikiPage.php:170
/workspace/src/includes/Page/Article.php:173
/workspace/src/includes/Page/Article.php:144
/workspace/src/extensions/MobileFrontend/tests/phpunit/integration/MobileFrontendHooksTest.php:522
[and another copy of this failure]I think this is because Wikibase CI pulls in the ParserMigration extension, which doesn’t seem to be enabled in MobileFrontend’s CI, so whatever the issue is, it wasn’t noticed in MobileFrontend itself.