Nokogiri custom pseudo selector

custom_pseudo_selector.rb

require 'nokogiri'

html_string = <<-HTML
<div id="columns">
  <div class="col1">
    <h4>October 01, 2014</h4><br />
    <a name="063579" class="random-named-link"></a>

    <h2>Some kind of heading</h2>
    Start of the text we want.<br />
    <br />
    More of the text we want. <br />
    <br />
    Last chunk of text we want.
    <p class="foo">Stuff we don't want.<br /></p>
    <a href="http://example.com">Some link we don't want</a>
    <div class="blah">
    More stuff we don't want. And a <a href="">link</a> to.
    </div>
    <br />
    <script src="http://somesocialtrackingwidget.com" type="text/javascript"></script>
    <!-- Loads more divs we don't want -->
  </div>

  <div class="col2">
    A whole column of stuff we don't want.
  </div>
</div>
HTML

def clean_whitespace(str)
  str.strip.gsub(/[[:space:]]/, ' ').gsub(/\s+/, ' ')
end

describe "#children_text_nodes" do
  let(:dom) { Nokogiri::HTML.parse(html_string) }

  let(:expected_result) do
    [
      'Start of the text we want.',
      'More of the text we want.',
      'Last chunk of text we want.'
    ].join(' ')
  end

  it "extracts the text nodes from the given node set (works)" do
    content_nodes = dom.css("#columns .col1:children_text_nodes", Class.new {
      def children_text_nodes(node_set)
        node_set.css('*').unlink
        node_set
      end
    }.new)

    results = content_nodes.collect{ |n| clean_whitespace(n.content) }.join(' ')
    expect(results).to eq(expected_result)
  end

  it "extracts the text nodes from the given node set (doesn't work)" do
    content_nodes = dom.css("#columns .col1:children_text_nodes", Class.new {
      def children_text_nodes(node_set)
        node_set.children.select{ |node| node.class == Nokogiri::XML::Text }
      end
    }.new)

    results = content_nodes.collect{ |n| clean_whitespace(n.content) }.join(' ')
    expect(results).to eq(expected_result)
  end
end

Gemfile

source 'https://rubygems.org'

gem "nokogiri", "1.6.1"
gem "rspec", "~>2.14.0"

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    diff-lcs (1.2.5)
    mini_portile (0.5.3)
    nokogiri (1.6.1)
      mini_portile (~> 0.5.0)
    rspec (2.14.1)
      rspec-core (~> 2.14.0)
      rspec-expectations (~> 2.14.0)
      rspec-mocks (~> 2.14.0)
    rspec-core (2.14.8)
    rspec-expectations (2.14.5)
      diff-lcs (>= 1.1.3, < 2.0)
    rspec-mocks (2.14.6)

PLATFORMS
  ruby

DEPENDENCIES
  nokogiri (= 1.6.1)
  rspec (~> 2.14.0)