haml_support.rb

# The idea for this technique taken from: http://blog.wolfman.com/articles/2007/07/14/using-rspec-to-test-haml-helpers
module HelperHamlSupport
  def new(*args, &block)
    super.tap do |obj|
      obj.extend Haml
      obj.extend Haml::Helpers
      obj.init_haml_helpers
    end
  end
end

Spec::Rails::Example::HelperExampleGroup::HelperObject.extend HelperHamlSupport