class Timecop

def travel(mock_type, *args, &block) #:nodoc:
  stack_item = TimeStackItem.new(mock_type, *args)
  # store this time traveling on our stack...
  @_stack << stack_item
  if block_given?
    begin
      yield stack_item.time
    ensure
      # pull it off the stack...
      @_stack.pop
    end
  end
end