# File lib/rails/dom/testing/assertions/selector_assertions.rb, line 250
        def assert_select_email(&block)
          deliveries = ActionMailer::Base.deliveries
          assert !deliveries.empty?, "No e-mail in delivery list"

          deliveries.each do |delivery|
            (delivery.parts.empty? ? [delivery] : delivery.parts).each do |part|
              if part["Content-Type"].to_s =~ /^text\/html\W/
                root = Nokogiri::HTML::DocumentFragment.parse(part.body.to_s)
                assert_select root, ":root", &block
              end
            end
          end
        end