Your requirements could not be resolved to an installable set of packages. Problem 1 - phpunit/phpunit dev-main requires php >=8.2 -> your php version (8.1.99; overridden via config.platform, actual: 8.2.15) does not satisfy that requirement. - phpunit/phpunit 11.1.x-dev is an alias of phpunit/phpunit dev-main and thus requires it to be installed too. - Root composer.json requires phpunit/phpunit ^11.0.0 -> satisfiable by phpunit/phpunit[11.0.0, ..., 11.1.x-dev (alias of dev-main)]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.