class RSpec::Core::ExampleGroup

def self.subclass(parent, description, args, registration_collection, &example_group_block)
  subclass = Class.new(parent)
  subclass.set_it_up(description, args, registration_collection, &example_group_block)
  subclass.module_exec(&example_group_block) if example_group_block
  # The LetDefinitions module must be included _after_ other modules
  # to ensure that it takes precedence when there are name collisions.
  # Thus, we delay including it until after the example group block
  # has been eval'd.
  MemoizedHelpers.define_helpers_on(subclass)
  subclass
end