class RSpec::Core::Notifications::SummaryNotification

def duplicate_rerun_locations
  @duplicate_rerun_locations ||= begin
    locations = RSpec.world.all_examples.map(&:location_rerun_argument)
    Set.new.tap do |s|
      locations.group_by { |l| l }.each do |l, ls|
        s << l if ls.count > 1
      end
    end
  end
end