test.rb

  def extract_highlights(highlighted_string)
    results = []

    str = highlighted_string.dup

    while start_index = str.index("<em>")
      match_length = str[start_index..-1].index("</em>") - 4

      results << [start_index, match_length]

      before_part = str[0...start_index]
      highlight_part = str[start_index + 4, match_length]
      after_part = str[start_index + 4 + match_length + 5..-1]
      str = [before_part, highlight_part, after_part].join
    end

    results
  end