Usage You need to tell RuboCop to load the Minitest extension. There are three ways to do this: RuboCop configuration file Put this into your .rubocop.yml. require: rubocop-minitest Now you can run rubocop and it will automatically load the RuboCop Minitest cops together with the standard cops. Command line $ rubocop --require rubocop-minitest Rake task RuboCop::RakeTask.new do |task| task.requires << 'rubocop-minitest' end Installation Cops