class Rspec::Core::ExampleGroup

def self.describe(*args, &behaviour_block)
  raise(ArgumentError, "No arguments given.  You must a least supply a type or description") if args.empty? 
  raise(ArgumentError, "You must supply a block when calling describe") if behaviour_block.nil?
  # TODO: Pull out the below into a metadata object, that we can defer the subclassing if necessary
  # describe 'foo', :shared => true will need this to be completed first
  subclass('NestedLevel') do
    args << {} unless args.last.is_a?(Hash)
    args.last.update(:behaviour_block => behaviour_block, :caller => caller(2))
    set_it_up(*args)
    module_eval(&behaviour_block)
  end
end