Before you contribute code to PHP_CodeSniffer, please make sure it conforms to the PHPCS coding standard and that the PHP_CodeSniffer unit tests still pass. The easiest way to contribute is to work on a checkout of the repository, or your own fork, rather than an installed PEAR version. If you do this, you can run the following commands to check if everything is ready to submit:
cd PHP_CodeSniffer
php bin/phpcs
Which should display no coding standard errors. And then:
phpunit
Which should give you no failures or errors. You can ignore any skipped tests as these are for external tools.