Simple Sinatra Server That Sets Cookies

cookie_server.rb

require "sinatra"
require "sinatra/cookies"

get '/' do
  "value: #{cookies[:something]}"
end

get '/set' do
  cookies[:something] = 'foobar'
  redirect to('/')
end

Gemfile

# frozen_string_literal: true
source "https://rubygems.org"

gem "sinatra"
gem "sinatra-contrib"

bundle install
ruby cookie_server.rb
Open localhost:4567/set in the browser to set the cookie and see it set upon redirection