Your requirements could not be resolved to an installable set of packages. Problem 1 - silverstripe/recipe-plugin[1.2.0, ..., 1.3.0] require composer-plugin-api ^1.1 -> found composer-plugin-api[2.6.0] but it does not match the constraint. - Root composer.json requires silverstripe/installer 4.11.x-dev -> satisfiable by silverstripe/installer[4.11.x-dev]. - You can only install one version of a package, so only one of these can be installed: silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev, 2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/recipe-testing[3.0.0, ..., 3.x-dev] require silverstripe/recipe-plugin ^2 -> satisfiable by silverstripe/recipe-plugin[2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/installer 4.11.x-dev requires silverstripe/recipe-plugin ^1.2 -> satisfiable by silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev]. - Root composer.json requires silverstripe/recipe-testing ^3 -> satisfiable by silverstripe/recipe-testing[3.0.0, 3.0.x-dev, 3.x-dev].

Your requirements could not be resolved to an installable set of packages. Problem 1 - silverstripe/recipe-plugin[1.2.0, ..., 1.3.0] require composer-plugin-api ^1.1 -> found composer-plugin-api[2.6.0] but it does not match the constraint. - Root composer.json requires silverstripe/installer 4.10.x-dev -> satisfiable by silverstripe/installer[4.10.x-dev]. - You can only install one version of a package, so only one of these can be installed: silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev, 2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/recipe-testing[3.0.0, ..., 3.x-dev] require silverstripe/recipe-plugin ^2 -> satisfiable by silverstripe/recipe-plugin[2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/installer 4.10.x-dev requires silverstripe/recipe-plugin ^1.2 -> satisfiable by silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev]. - Root composer.json requires silverstripe/recipe-testing ^3 -> satisfiable by silverstripe/recipe-testing[3.0.0, 3.0.x-dev, 3.x-dev].

Your requirements could not be resolved to an installable set of packages. Problem 1 - silverstripe/recipe-plugin[1.2.0, ..., 1.3.0] require composer-plugin-api ^1.1 -> found composer-plugin-api[2.6.0] but it does not match the constraint. - Root composer.json requires silverstripe/installer 4.9.x-dev -> satisfiable by silverstripe/installer[4.9.x-dev]. - You can only install one version of a package, so only one of these can be installed: silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev, 2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/recipe-testing[3.0.0, ..., 3.x-dev] require silverstripe/recipe-plugin ^2 -> satisfiable by silverstripe/recipe-plugin[2.0.0-alpha1, 2.0.0, 2.0.x-dev, 2.x-dev]. - silverstripe/installer 4.9.x-dev requires silverstripe/recipe-plugin ^1.2 -> satisfiable by silverstripe/recipe-plugin[1.2.0, ..., 1.x-dev]. - Root composer.json requires silverstripe/recipe-testing ^3 -> satisfiable by silverstripe/recipe-testing[3.0.0, 3.0.x-dev, 3.x-dev].