HTML5 Validator Gem

September 10 2011

We all know the benefits of adhering to web standards, but I’m sure you’ll agree it’s a laborious process manually checking the validity of each page within a site or web app using the online W3C validation service or a browser extension.

In an effort to scratch my own itch, I built a gem called html5_validator. It’s geared to run as part of an RSpec test suite, so if your serious about being standards compliant, you shouldn’t mind your tests failing if you’ve got some grubby HTML kicking about.

It can be installed using the following command.

gem install html5_validator

What’s cool is that if your page isn’t compliant resulting in a failing spec, the offending HTML is printed out as part of the failing test. See below an example of how this can be used in a controller test:

describe PostsController do

  it "should be valid html5" do
    get :new
    response.body.should be_valid_html5


How does this work?

I wrote a wrapper around an online HTML5 validation service called When run as part of an RSpec suite, the rendered HTML is posted to their web service which responds with some JSON containing the results of the validation check.

I opted to use over the official W3C validator because it supports JSON (the W3C only supports SOAP), so it’s easy to work with in Ruby.

More info

You can find the code on my Github repository along with a few more examples.

As always questions and comments are very welcome. Forks and pull requests even more so.