Fibonacci voting

voting.rb

class Fibonacci
  class << self
    def number(n)
      return cache[n] if cache[n]
     
      cache[n] = number(n-1) + number(n-2)
    end

    private

      def cache
        @cache ||= [0, 1]
      end
  end
end

class Voting
  def initialize(processor:)
    raise(ArgumentError, 'Processor object must respond to :number method') unless processor.respond_to?(:number)

    @processor = processor
  end

  def vote
    @processor.number(ballot)
  end

  private

    def ballot
      (1..4).to_a.sample
    end
end

Voting.new(processor: Fibonacci).vote

Here is a quick voting system which will always vote from 1 to 3, using Fibonacci sequence as an internal processor