Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ~9 -> satisfiable by phpunit/phpunit[9.6.33, 9.6.34]. - phpunit/phpunit[9.6.33, ..., 9.6.34] require myclabs/deep-copy ^1.13.4 -> found myclabs/deep-copy[1.13.4] but the package is fixed to 1.11.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. Problem 2 - dms/phpunit-arraysubset-asserts is locked to version v0.5.0 and an update of this package was not requested. - dms/phpunit-arraysubset-asserts v0.5.0 requires phpunit/phpunit ^4.8.36 || ^5.7.21 || ^6.0 || ^7.0 || ^8.0 || ^9.0 || ^10.0 -> satisfiable by phpunit/phpunit[9.6.33, 9.6.34]. - phpunit/phpunit[9.6.33, ..., 9.6.34] require myclabs/deep-copy ^1.13.4 -> found myclabs/deep-copy[1.13.4] but the package is fixed to 1.11.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.