Your requirements could not be resolved to an installable set of packages.
Problem 1
- phpunit/phpunit[7.5.0, ..., 7.5.20] require php ^7.1 -> your php version (8.1.2) does not satisfy that requirement.
- Root composer.json requires phpunit/phpunit ^7.5 -> satisfiable by phpunit/phpunit[7.5.0, ..., 7.5.20].