module Rspec::Core::SharedExampleGroup

def self.included(kls)
  kls.module_eval(&@shared_block)
end

def ensure_shared_example_group_name_not_taken(name)
  if Rspec::Core.world.shared_example_groups.has_key?(name)
    raise ArgumentError.new("Shared example group '#{name}' already exists")
  end
end

def share_as(name, &block)
  if Object.const_defined?(name)
    raise NameError, "The first argument (#{name}) to share_as must be a legal name for a constant not already in use."
  end
  
  mod = Module.new do
    @shared_block = block
    def self.included(kls)
      kls.module_eval(&@shared_block)
    end
  end
  shared_const = Object.const_set(name, mod)
  Rspec::Core.world.shared_example_groups[shared_const] = block
end

def share_examples_for(name, &block)
  ensure_shared_example_group_name_not_taken(name)
  Rspec::Core.world.shared_example_groups[name] = block
end