resque_retry_spec.rb

# spec/support/resque_helper.rb
module ResqueHelper
  def create_worker( queue_name )
    Resque.redis.flushall
    @worker = Resque::Worker.new( queue_name )
    @worker.register_worker
    return @worker
  end

  def perform_next_job(worker, &block)
    return unless job = worker.reserve
    worker.perform(job, &block)
    worker.done_working
  end
end

RSpec.configure do |config|
  config.include ResqueHelper
end

# your_spec.rb
it "Should retry in 10 seconds" do
  allow( SomeJob ).to receive( :perform ).and_raise( Exception )

  Resque.enqueue( SomeJob, "Lorem", "Ipsum" )
  @worker = create_worker( :queue_name )
  perform_next_job( @worker )

  expect( SomeJob ).to have_scheduled(
    "Lorem", "Ipsum"
  ).in( 10.seconds )
end