Can we automatically check that some pages have a valid HTML markup ? This can be useful as part of a CI process, or for an automated audit.

A solution

The W3C provides an online validation tool. It turns out it is packaged as a docker container, and there are Ruby bindings to communicate with this service. Here is an example.

• Run the W3C validator as a docker container

docker run -it --rm -p 8888:8888 ghcr.io/validator/validator:latest

• Install the w3c_validators ruby gem.

# Gemfile
source "https://rubygems.org"
gem 'w3c_validators'

bundle install

• Run the audit. In my case, the list of URLs I wanted to check came from a yaml file. I do not use the results.errors array, but it contains the error messages and locations.

# audit.rb
require 'w3c_validators'
require 'yaml'

include W3CValidators

validator = NuValidator.new(:validator_uri => 'http://localhost:8888/')

url_db = YAML.load_file('data/urls.yml')

invalid = []

url_db['urls'].each do |se|
	uri = se['url']

	results = validator.validate_uri(uri)
	if results.errors.length > 0
		invalid << uri
	end
end

puts invalid

ruby audit.rb

This is not necessarily convenient, but all this can be automated as part of a test suite inside a CI.