Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires infection/infection ^0.26.19 -> satisfiable by infection/infection[0.26.19, 0.26.20, 0.26.21, 0.26.x-dev]. - Root composer.json requires phpunit/phpunit ^12.0.7 -> satisfiable by phpunit/phpunit[12.0.7, 12.0.x-dev, 12.1.x-dev]. - infection/infection[0.26.19, ..., 0.26.x-dev] require sebastian/diff ^3.0.2 || ^4.0 || ^5.0 -> satisfiable by sebastian/diff[3.0.2, ..., 3.0.x-dev, 4.0.0, ..., 4.0.x-dev, 5.0.0, ..., 5.1.x-dev]. - phpunit/phpunit[12.0.7, ..., 12.1.x-dev] require sebastian/diff ^7.0.0 -> satisfiable by sebastian/diff[7.0.0, 7.0.x-dev]. - sebastian/diff 3.0.2 requires php ^7.1 -> your php version (8.3.16) does not satisfy that requirement. - sebastian/diff[4.0.0, ..., 4.0.1] require php ^7.3 -> your php version (8.3.16) does not satisfy that requirement. - You can only install one version of a package, so only one of these can be installed: sebastian/diff[3.0.2, ..., 3.0.x-dev, 4.0.0, ..., 4.0.x-dev, 5.0.0, ..., 5.1.x-dev, 7.0.0, 7.0.x-dev]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.