# Note: this delegator has a __getobj__ method but no __setobj__
class TestClass < Delegator
  def initialize obj
    @obj = obj
  end

  def __getobj__
    @obj
  end
end

Kernel.delay.puts(TestClass.new('foo'))
Delayed::Worker.new.work_off
# => NotImplementedError: need to define `__setobj__'
#    from /Users/afn/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/delegate.rb:168:in `__setobj__'