cli_spec_example.rb

    let(:app) do
      CLIWrapper.new do |stdin, stdout|
        prompt = TTY::Prompt.new(input: stdin, output: stdout)

        prompt.yes?('Do you like Ruby?')

        prompt.collect do
          key(:name).ask('Name?')
          key(:age).ask('Age?', convert: :int)
        end

        prompt.select("Choose your destiny?", %w(Scorpion Kano Jax))

        # ...
      end
    end

    before { app.run! }

    it 'asks a series of questions' do
      expect(app.stdout.string).to end_with('Do you like Ruby? (Y/n) ')
      app.stdin.puts 'y'

      app.resume_execution!

      expect(app.stdout.string).to end_with('Name? ')
      app.stdin.puts 'John'

      app.resume_execution!

      expect(app.stdout.string).to end_with('Age? ')
      app.stdin.puts '22'

      app.resume_execution!

      expect(app.stdout.string).to end_with(
"Choose your destiny? (Use ↑/↓ arrow keys, press Enter to select)
‣ Scorpion
  Kano
  Jax")

      app.stdin.puts "\e[B\e[B" # arrow down twice

      app.resume_execution!

      # ...
    end

cli_wrapper.rb

    class CLIWrapper
      def initialize(&block)
        @stdout = StringIO.new

        @stdin_reader, @stdin_writer = IO.pipe

        @fiber = Fiber.new do
          block.call(@stdin_reader, @stdout)
        end

        @stdin_reader.singleton_class.define_method(:getc) do
          char = read_nonblock(1, exception: false)
          if char.is_a?(String)
            char
          else
            Fiber.yield
            getc
          end
        end
      end

      def resume_execution!
        @fiber.resume
      end
      alias run! resume_execution!

      def stdin
        @stdin_writer
      end

      def stdout
        @stdout
      end
    end