bridge.rb

class Posts
  cattr_accessor :source

  def initialize
    @client = source.new
  end

  def posts(args)
    @client.user_posts(args)
  end
end

module PostsSources
  class Medium
    def initialize
      @client = MediumApi.new(access_token)
    end

    def user_posts(args)
      @client.posts(args)
    end
  end
end

module PostsSources
  class Fake
    def initialize
      @client = OpenStruct.new(
        posts: [{
          "title": "Liverpool FC",
          "contentFormat": "html",
          "content": "<h1>Liverpool FC</h1><p>You’ll never walk alone.</p>",
          "canonicalUrl": "http://jamietalbot.com/posts/liverpool-fc",
          "tags": ["football", "sport", "Liverpool"],
          "publishStatus": "public"
        }]
      )
    end

    def user_posts(args)
      @client.posts
    end
  end
end