Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires http-interop/http-factory-tests ^0.9.0 -> satisfiable by http-interop/http-factory-tests[0.9.0]. - http-interop/http-factory-tests 0.9.0 requires phpunit/phpunit ^6.5 || ^7.0 || ^8.0 || ^9.0 -> found phpunit/phpunit[6.5.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.36, 9.0.0, ..., 9.6.16] but it conflicts with your root composer.json require (^11.0.0). Problem 2 - Root composer.json requires php-http/psr7-integration-tests ^1.3 -> satisfiable by php-http/psr7-integration-tests[1.3.0]. - php-http/psr7-integration-tests 1.3.0 requires phpunit/phpunit ^8.0 || ^9.3 -> found phpunit/phpunit[8.0.0, ..., 8.5.36, 9.3.0, ..., 9.6.16] but it conflicts with your root composer.json require (^11.0.0). Problem 3 - sebastian/diff[4.0.0, ..., 4.0.1] require php ^7.3 -> your php version (8.2.15) does not satisfy that requirement. - Root composer.json requires phpunit/phpunit ^11.0.0 -> satisfiable by phpunit/phpunit[11.0.0]. - psalm/plugin-phpunit 0.18.4 requires vimeo/psalm dev-master || dev-4.x || ^4.7.1 || ^5@beta || ^5.0 -> satisfiable by vimeo/psalm[5.17.0, ..., 5.21.1]. - vimeo/psalm[5.17.0, ..., 5.21.1] require sebastian/diff ^4.0 || ^5.0 -> satisfiable by sebastian/diff[4.0.0, ..., 4.0.5, 5.0.0, ..., 5.1.0]. - You can only install one version of a package, so only one of these can be installed: sebastian/diff[4.0.0, ..., 4.0.5, 5.0.0, ..., 5.1.0, 6.0.0]. - phpunit/phpunit 11.0.0 requires sebastian/diff ^6.0 -> satisfiable by sebastian/diff[6.0.0]. - Root composer.json requires psalm/plugin-phpunit ^0.18.4 -> satisfiable by psalm/plugin-phpunit[0.18.4]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.