spec.rb

class SomeScraper
  def initialize(document)
    @document = document
  end

  def parse
    return @document.at('p.foo').text
  end
end

# some_scraper_spec.rb

describe SomeScraper do
  before do
    node     = double(:node, :text => 'Foo')
    document = double(:document, :at => node)
    @scraper = described_class.new(document)
  end

  example 'return the text' do
    @scraper.parse.should == 'Foo'
  end
end