Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires phpunit/phpunit ^11.2.9 -> satisfiable by phpunit/phpunit[11.2.9, 11.2.x-dev, 11.3.x-dev].
- phpunit/phpunit[11.2.9, ..., 11.3.x-dev] require php >=8.2 -> your php version (8.1.29) does not satisfy that requirement.
Problem 2
- orchestra/testbench[v8.0.0, ..., v8.3.1] require phpunit/phpunit ^9.6 || ^10.0.7 -> found phpunit/phpunit[9.6.0, ..., 9.6.x-dev, 10.0.7, ..., 10.5.x-dev] but it conflicts with your root composer.json require (^11.2.9).
- orchestra/testbench[v8.4.0, ..., 8.x-dev] require phpunit/phpunit ^9.6 || ^10.1 -> found phpunit/phpunit[9.6.0, ..., 9.6.x-dev, 10.1.0, ..., 10.5.x-dev] but it conflicts with your root composer.json require (^11.2.9).
- Root composer.json requires orchestra/testbench ^8.0 -> satisfiable by orchestra/testbench[v8.0.0, ..., 8.x-dev].