After installing a brand new copy of MW from current head at b347d8e I ran php maintenance/update.php followed by php tests/phpunit/phpunit.php --tap tests/phpunit/includes/resourceloader/MessageBlobStoreTest.php and got the following failure message:
php tests/phpunit/phpunit.php --tap tests/phpunit/includes/resourceloader/MessageBlobStoreTest.php Using PHP 7.0.22-0ubuntu0.16.04.1 TAP version 13 ok 1 - MessageBlobStoreTest::testSetLogger ok 2 - MessageBlobStoreTest::testGetResourceLoader ok 3 - MessageBlobStoreTest::testFetchMessage ok 4 - MessageBlobStoreTest::testFetchMessageFail ok 5 - MessageBlobStoreTest::testGetBlob not ok 6 - Failure: MessageBlobStoreTest::testGetBlobCached --- message: 'MessageBlobStore::fetchMessage(''example'', ''en'') was not expected to be called.' severity: fail ... ok 7 - MessageBlobStoreTest::testUpdateMessage ok 8 - MessageBlobStoreTest::testValidation ok 9 - MessageBlobStoreTest::testClear 1..9
This is a brand new installation of MediaWiki with no extensions whatsoever, and with no caching installed (e.g. no memcahced, etc.) so I would expect that test to either pass or be skipped, depending on what is intended behavior.