Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^12.2 -> satisfiable by phpunit/phpunit[12.2.0, ..., 12.3.x-dev (alias of dev-main)]. - phpunit/phpunit[dev-main, 12.2.0, ..., 12.2.2] require php >=8.3 -> your php version (8.2.28) does not satisfy that requirement. - phpunit/phpunit 12.3.x-dev is an alias of phpunit/phpunit dev-main and thus requires it to be installed too.