Tiny rack app to fake a JSON API

fake_api.rb

require 'json'

class MyApp
  def call(env)
    request = Rack::Request.new(env)
    headers = {
      'Content-Type' => 'application/json',
      'Access-Control-Allow-Origin' => '*',
    }

    case request.path
    when '/medal-table.json'
      json = {
        table: [
          { countryName: "United States of America", gold: 39, silver: 41, bronze: 33 },
          { countryName: "People's Republic of China", gold: 38, silver: 32, bronze: 19 },
          { countryName: "ROC", gold: 20, silver: 28, bronze: 23 }
        ]
      }.to_json
      [200, headers, [json]]
    else
      [404, headers, [{ error: 404 }.to_json]]
    end
  end
end

run MyApp.new

Run with rackup/puma etc.