Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires infection/infection ^0.29.9 -> satisfiable by infection/infection[0.29.9]. - infection/infection 0.29.9 requires thecodingmachine/safe dev-master as 2.5.0 -> found thecodingmachine/safe[dev-master] but it does not match your minimum-stability. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.