Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit 7.5.20 (exact version match: 7.5.20 or 7.5.20.0), found phpunit/phpunit[7.5.20] but these were not loaded, because they are affected by security advisories ("PKSA-z3gr-8qht-p93v"). Go to https://packagist.org/security-advisories/ to find advisory details. To ignore the advisories, add them to the audit "ignore" config. To turn the feature off entirely, you can set "block-insecure" to false in your "audit" config. Problem 2 - Root composer.json requires brianium/paratest 4.0 -> satisfiable by brianium/paratest[4.0.0]. - brianium/paratest 4.0.0 requires phpunit/phpunit ^7.5.8|^8.0|^9.0 -> found phpunit/phpunit[7.5.8, ..., 7.5.20, 8.0.0, ..., 8.5.x-dev, 9.0.0, ..., 9.6.x-dev] but these were not loaded, because they are affected by security advisories ("PKSA-z3gr-8qht-p93v"). Go to https://packagist.org/security-advisories/ to find advisory details. To ignore the advisories, add them to the audit "ignore" config. To turn the feature off entirely, you can set "block-insecure" to false in your "audit" config. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.