If you run phpunit with the -v argument, you'll get this error: Undefined index: quiet squizlabs/php_codesniffer/CodeSniffer/CLI.php:488 squizlabs/php_codesniffer/CodeSniffer/CLI.php:458 squizlabs/...

Undefined index: quiet in CLI.php during unit test run with -v command line arg · Issue #1066 · squizlabs/PHP_CodeSniffer