Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpspec/prophecy-phpunit ^2.0.1 -> satisfiable by phpspec/prophecy-phpunit[v2.0.1, v2.0.2]. - phpspec/prophecy-phpunit[v2.0.1, ..., v2.0.2] require phpunit/phpunit ^9.1 -> found phpunit/phpunit[9.1.0, ..., 9.6.10] but it conflicts with your root composer.json require (^10.0.0). Problem 2 - phpunit/phpunit[10.0.0, ..., 10.2.4] require php >=8.1 -> your php version (8.0.26) does not satisfy that requirement. - Root composer.json requires phpunit/phpunit ^10.0.0 -> satisfiable by phpunit/phpunit[10.0.0, ..., 10.2.4]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.