Change CLI#recipe as read-only attribute

lib/producer/core/cli.rb

@@ -19,8 +19,7 @@ module Producer
         end
       end
 
-      attr_reader :arguments, :stdout
-      attr_accessor :recipe
+      attr_reader :arguments, :stdout, :recipe
 
       def initialize(arguments, stdout: $stdout)
         raise ArgumentError unless arguments.any?

spec/producer/core/cli_spec.rb

@@ -72,7 +72,7 @@ module Producer::Core
     describe '#recipe' do
       it 'returns the assigned recipe' do
         recipe = double 'recipe'
-        cli.recipe = recipe
+        cli.instance_eval { @recipe = recipe }
         expect(cli.recipe).to be recipe
       end
     end