Delayed Job Queue Adapter in RSpec with Rails 5.1

In old versions of Rails, you were able to override the ActiveJob queue in a test like this:

describe MyJob do
  it 'works' do
    ActiveJob::Base.queue_adapter = :delayed_job
    expect {
      MyJob.perform_later(some_params)
    }.to change(Delayed::Job.count).by(1)
  end
end

With Rails 5.1, we have the ActiveJob::TestHelper class which you will need to employ in your tests. In order to override the queue a different strategy is needed.

describe MyJob do
  def queue_adapter_for_test
    ActiveJob::QueueAdapters::DelayedJobAdapter.new
  end
  
  it 'works' do
    expect {
      MyJob.perform_later(some_params)
    }.to change(Delayed::Job.count).by(1)
  end
end

You will need to add the following to your rspec config or a support file:

RSpec.configure do |config|
  config.include(ActiveJob::TestHelper)
end

# you will also need the code below for the test
# to clear out the jobs between test runs
class ActiveJob::QueueAdapters::DelayedJobAdapter
  class EnqueuedJobs
    def clear
      Delayed::Job.where(failed_at:nil).map &:destroy
    end
  end
  
  class PerformedJobs
    def clear
      Delayed::Job.where.not(failed_at:nil).map &:destroy
    end
  end
  
  def enqueued_jobs
    EnqueuedJobs.new
  end
  
  def performed_jobs
    PerformedJobs.new
  end
end