cursor.rb

class Cursor
  include Enumerable

  def each
    p "cursor #{Thread.current.object_id}"
    yield(1)
    yield(2)
  end
end

p "main #{Thread.current.object_id}"
e = Cursor.new.to_enum
e.next

MRI result:

"main 70247306709460"
"cursor 70247306709460"

JRuby result:

"main 2000"
"cursor 2002"