Robust CSV Importer

csv_importer.rb

class CsvImporterJob < ApplicationJob
  queue_as :default
  
  # Handle any cleanup after perform
  after_perform { |job| clean_up_csv_upload(job) }

  def perform(file, user)
    # Use begin/rescue - raise StandardError in importer if something goes wrong 
    # Rescue here with email notification to user
    begin
      CsvImporter.import(file, user)
      NotificationMailer.csv_import_successful(user).deliver_later
    rescue StandardError => error
      NotificationMailer.csv_import_failed(user, error.message).deliver_later
    end
  end

  def clean_up_csv_upload(job)
    # Clean up the file from ActiveStorage
    csv_upload = job.arguments.first
    csv_upload.destroy
  end
end

Ensure csv upload model purges on destroy...

class CsvUpload < ApplicationRecord
  belongs_to :user
  has_one_attached :file

  before_destroy :purge_attachment

  def purge_attachment
    self.file.purge
  end
end

Tests for this Job...

require 'rails_helper'

RSpec.describe CsvImporterJob, type: :job do
  include ActiveJob::TestHelper

  let!(:user)             { FactoryBot.create(:user) }
  let!(:csv_upload)  { FactoryBot.create(:csv_upload, user: user) }

  subject(:job) { described_class.perform_later(csv_upload) }

  describe '.perform' do
    it 'calls CsvImporter.import' do
      expect(CsvImporter).to receive(:import).with(csv_upload)
      perform_enqueued_jobs { job }
    end

    context 'when successful' do
      it 'sends csv_import_successful mailer' do
        expect_any_instance_of(NotificationMailer).to receive(:csv_import_successful).with(user)
        allow(CsvImporter).to receive(:import).with(csv_upload)
        perform_enqueued_jobs { job }
      end
    end

    context 'when failed' do
      it 'sends csv_import_failed mailer' do
        expect_any_instance_of(NotificationMailer).to receive(:csv_import_failed).with(user, 'oh no!')
        allow(CsvImporter).to receive(:import).with(csv_upload).and_raise(StandardError, 'oh no!')
        perform_enqueued_jobs { job }
      end
    end
  end

  describe 'callbacks' do
    describe 'after_perform' do
      it 'deletes the CsvUpload' do
        expect {
          allow(CsvImporter).to receive(:import).with(csv_upload)
          perform_enqueued_jobs { job }
        }.to change(CsvUpload, :count).by(-1)
      end
    end
  end

  after do
    clear_enqueued_jobs
    clear_performed_jobs
  end
end

And for mailers...

require 'rails_helper'

RSpec.describe NotificationMailer, type: :mailer do
  let(:user) { FactoryBot.create(:user) }

  describe '#csv_import_successful' do
    let(:mail) { NotificationMailer.csv_import_successful(user) }

    it 'renders the headers' do
      expect(mail.subject).to eq('Import successful')
      expect(mail.to).to eq([user.email])
    end

    it 'renders the body' do
      expect(mail.body.encoded).to match('Your csv has been imported!')
    end
  end

  describe '#csv_import_failed' do
    let(:mail) { NotificationMailer.csv_import_failed(user, 'error message') }

    it 'renders the headers' do
      expect(mail.subject).to eq('Import failed')
      expect(mail.to).to eq([user.email])
    end

    it 'renders the body' do
      expect(mail.body.encoded).to match('Something went wrong')
    end
  end
end