Run composer install
Run php ./vendor/bin/simple-phpunit
PHPUnit 9.5.10 by Sebastian Bergmann and contributors.
Warning: Your XML configuration validates against a deprecated schema.
Suggestion: Migrate your XML configuration using "--migrate-configuration"!
Testing
PHP Fatal error: Cannot declare interface PhpParser\Parser, because the name is already in use in /home/gabriel/personal/rector-phpunit-bug/vendor/rector/rector/vendor/nikic/php-parser/lib/PhpParser/Parser.php on line 6