Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires spatie/phpunit-snapshot-assertions ^5.0 -> satisfiable by spatie/phpunit-snapshot-assertions[5.0.0, ..., 5.1.7]. - Root composer.json requires vimeo/psalm ~4.30.0 -> satisfiable by vimeo/psalm[4.30.0]. - phpunit/phpunit[10.0.0, ..., 10.5.26] require sebastian/diff ^5.0 -> satisfiable by sebastian/diff[5.0.0, ..., 5.1.x-dev]. - phpunit/phpunit[10.5.27, ..., 10.5.x-dev] require sebastian/diff ^5.1.1 -> satisfiable by sebastian/diff[5.1.1, 5.1.x-dev]. - phpunit/phpunit[11.0.0, ..., 11.5.x-dev] require php >=8.2 -> your php version (8.1.31) does not satisfy that requirement. - spatie/phpunit-snapshot-assertions[5.0.0, ..., 5.1.3] require phpunit/phpunit ^10.0 -> satisfiable by phpunit/phpunit[10.0.0, ..., 10.5.x-dev]. - spatie/phpunit-snapshot-assertions[5.1.4, ..., 5.1.7] require phpunit/phpunit ^10.0|^11.0 -> satisfiable by phpunit/phpunit[10.0.0, ..., 10.5.x-dev, 11.0.0, ..., 11.5.x-dev]. - Conclusion: don't install sebastian/diff 5.1.1 (conflict analysis result)