Given a CSV file with expected redirects - verify that each redirect is performed correctly.

check_redirect.rb

#!/usr/bin/env ruby

# USAGE:
#   $ check_redirects --help
#   or
#   $ ruby check_redirects.rb --help

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'honey_format', '~> 0.18'
  gem 'http', '~> 3.3'
end

require 'optparse'
require 'honey_format'
require 'http'

class RedirectChecker
  attr_reader :results, :domain

  def check(from_url, expected_to)
    @results ||= []
    url = to_url(from_url)
    expected = remove_spaces(expected_to)&.force_encoding('UTF-8')

    response = Http.get(url)
    # Paths can contain scary characters: 'sa-far-du-ersatt\xE2\x80\xA6marens-flygstrul/'
    location = response.headers['Location']&.force_encoding('UTF-8')

    success = location == expected # if both are nil - no redirect is the success case
    unless success
      loc_part = location ? "instead redirected to #{location}" : "didn't redirect"
      puts "[FAILED] #{url} should redirect to #{expected} but #{loc_part}."
    end
    [success, url, location, expected].tap { |r| @results << r }
  end

  private

  def remove_spaces(string)
    string.to_s.gsub(/[[:space:]]/, '')
  end

  def to_url(url, scheme: 'http://')
    url = remove_spaces(url)
    return url if %w[http:// https://].any? { |s| url.start_with?(s) }

    "#{scheme}#{url}"
  end
end

options = {}
OptionParser.new do |parser|
  parser.banner = 'Usage: ruby check_redirects.rb --help'
  parser.default_argv = ARGV

  parser.on('--input=val0', String, 'CSV file path (required) - must be a file with two columns: from_url, to_url') do |string|
    options[:input] = string
  end

  parser.on('--output=val0', String, 'CSV output path (optional)') do |string|
    options[:output] = string
  end

  parser.on('-h', '--help', 'How to use') do
    puts parser
    exit
  end
end.parse!

input_path = options[:input] || fail(ArgumentError, '--input required - CSV file path must be provided')
output_path = options[:output] || input_path.gsub(/\.csv/, '-redirect-results.csv')

puts "=== [CheckRedirect] Reading input file #{input_path} ==="
checker = RedirectChecker.new
input_csv = HoneyFormat::CSV.new(File.read(input_path))
puts "=== [CheckRedirect] Going to check #{input_csv.rows.length} redirects ==="

header = %w[success from redirected_to expected_redirect]
rows = input_csv.rows.map { |row| checker.check(row.from_url, row.to_url) }
output_csv = HoneyFormat::Matrix.new(rows, header: header).to_csv

File.write(output_path, output_csv)
puts "=== [CheckRedirect] Wrote output to #{output_path} ==="