class RSpec::Core::SharedExampleGroup::Registry

def add_group(source, *args, &block)
  ensure_block_has_source_location(block, caller[1])
  if key? args.first
    key = args.shift
    warn_if_key_taken source, key, block
    add_shared_example_group source, key, block
  end
  unless args.empty?
    mod = Module.new
    (class << mod; self; end).send :define_method, :extended  do |host|
      host.class_eval(&block)
    end
    RSpec.configuration.extend mod, *args
  end
end