On master branch of MediaWiki, MSCompoundFileReaderTest is failing when executed on macOS:
$ php tests/phpunit/phpunit.php --filter MSCompoundFileReaderTest Using PHP 7.3.5 PHPUnit 6.5.14 by Sebastian Bergmann and contributors. FFFFFFF... 10 / 10 (100%) Time: 6.67 seconds, Memory: 257.00MB There were 7 failures: 1) MSCompoundFileReaderTest::testReadFile with data set #0 ('calc.xls', 'application/vnd.ms-excel') Failed asserting that null is identical to 'application/vnd.ms-excel'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 2) MSCompoundFileReaderTest::testReadFile with data set #1 ('excel2016-compat97.xls', 'application/vnd.ms-excel') Failed asserting that null is identical to 'application/vnd.ms-excel'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 3) MSCompoundFileReaderTest::testReadFile with data set #2 ('gnumeric.xls', 'application/vnd.ms-excel') Failed asserting that null is identical to 'application/vnd.ms-excel'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 4) MSCompoundFileReaderTest::testReadFile with data set #3 ('impress.ppt', 'application/vnd.ms-powerpoint') Failed asserting that null is identical to 'application/vnd.ms-powerpoint'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 5) MSCompoundFileReaderTest::testReadFile with data set #4 ('powerpoint2016-compat97.ppt', 'application/vnd.ms-powerpoint') Failed asserting that null is identical to 'application/vnd.ms-powerpoint'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 6) MSCompoundFileReaderTest::testReadFile with data set #5 ('word2016-compat97.doc', 'application/msword') Failed asserting that null is identical to 'application/msword'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 7) MSCompoundFileReaderTest::testReadFile with data set #6 ('writer.doc', 'application/msword') Failed asserting that null is identical to 'application/msword'. /Users/mateszabo/Wikia/mediawiki/tests/phpunit/includes/libs/mime/MSCompoundFileReaderTest.php:40 /Users/mateszabo/Wikia/mediawiki/maintenance/doMaintenance.php:99 FAILURES! Tests: 10, Assertions: 20, Failures: 7.
The test passes when run in a Linux VM or the WM CI environment. The test or the underlying class should be fixed so that it consistently passes on all environments.