Your requirements could not be resolved to an installable set of packages. Problem 1 - orchestra/testbench[v8.5.7, ..., v8.5.12] require orchestra/testbench-core >=8.5.7 <8.6.0 -> found orchestra/testbench-core[v8.5.7, v8.5.8, v8.5.9] but it conflicts with your root composer.json require (8.x-dev). - orchestra/testbench v8.6.0 requires orchestra/testbench-core >=8.6.0 <8.7.0 -> found orchestra/testbench-core[v8.6.0] but it conflicts with your root composer.json require (8.x-dev). - Root composer.json requires orchestra/testbench >=8.5.7 <8.7.0 -> satisfiable by orchestra/testbench[v8.5.7, ..., v8.6.0].