Uses the frozen_string_literal magic comment (will be the default in Ruby 3)

spec/lib/target_spec.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe WPScan::Target do
   subject(:target) { described_class.new(url) }
   let(:url)        { 'http://ex.lo' }