XPath matcher using nokogiri.

document_spec.rb

require 'nokogiri'

RSpec::Matchers.define :have_xpath do |*paths|
  match do |doc|
    !doc.xpath(*paths).empty?
  end
end

def within *paths, &block
  describe "within #{paths.inspect}" do
    self.class.class_eval do
      define_method :subject do
        super().xpath *paths
      end
    end
  end
end

describe 'some document' do
  subject { Nokogiri.XML('<foo><bar /><foo>') }

  it { should have_xpath '//bar' }

  it { should_not have_xpath '//baz' }

  within '//foo' do
    it { should have_xpath '//bar' }
  end
end