npm install w3cjs

var w3cjs = require('w3cjs');

var results = w3cjs.validate({
	file: 'demo.html', // file can either be a local file or a remote file
	//file: 'http://html5boilerplate.com/',
	output: 'json', // Defaults to 'json', other option includes html
	callback: function (res) {
		console.log(res);
		// depending on the output type, res will either be a json object or a html string
	}
});

var w3cjs = require('w3cjs');
describe('html validation', function(){
  it('index page should have no html errors', function(done){
  	w3cjs.validate({
  		file: 'index.html',
  		callback: function (res) {
  				console.log(res);
  			if (res.messages.length > 0 ) {
  				throw {error: 'html errors have been found', results: res};
  			};
  			done();
  		}
  	})
  })
})