Testing asynchronous methods and behavior with Rails, DelayedJob, and Rspec

job.rb

class SomeJob
  attr_accessor :some_model

  def initialize(some_model_id)
    self.some_model = SomeModel.find(some_model_id)
  end

  def perform
    some_model.do_stuff
  end
end

some_model.rb

class SomeModel < ActiveRecord::Base
  after_save :delay_do_stuff!
  
  def do_stuff
    # ...
  end
  
  private
  
  def delay_do_stuff
    Delayed::Job.enqueue(id) if stuff
  end
end

some_model_spec.rb

require 'spec_helper'

describe SomeModel, type: :model do

  it 'delays do_stuff after save' do
    expect(some_model).to receive(:delay_do_stuff)
    some_model.run_callbacks(:save)
  end
  
  describe '#do_stuff' do
    # Test do_stuff behavior...
  end
end