foo.rb

require 'fiber'

class Job
  include Enumerable

  def initialize(jobs)
    @jobs = jobs
  end

  def each(&block)
    @jobs.each(&block)
  end

  def next
    @fiber ||= Fiber.new do
      each { |e| Fiber.yield e }

      raise StopIteration
    end

    @fiber.resume
  end
end

require 'minitest/autorun'

describe Job do
  it "should be iterable" do
    job = Job.new([1,2,3])
    assert_equal job.next, 1
    assert_equal job.next, 2
    assert_equal job.next, 3
    -> { job.next }.must_raise StopIteration
  end
end