In my Rails 6 app I want to write MiniTest for a service which is responsible for creating CSV files. I found few examples (like here) of how to do it when the services responsible for it use CSV.open instead of CSV.generate like mine. I've below code:

# services/csv_log_generator
class CsvLogGenerator
  LOG_HEADERS = ['Created at', 'Action Type', 'Acting User', 'New Data'].freeze

  def call
    CSV.generate(col_sep: ';', write_headers: true, headers: LOG_HEADERS, encoding: 'UTF-8') do |csv|
      PaperTrail::Version.includes([:item]).where(item_type: 'CashTransaction').limit(99).order(id: :desc).each do |v|
        tracked_data(v)
        csv << [v.created_at.in_time_zone('London'),
                v.event,
                user_name(v),
                @new_data_value]
      end
    end
  end

# csv_log_generator_test
class CsvLogGeneratorTest < ActiveSupport::TestCase
 setup do
   Book.create!(title: 'title')
   service.call
 end

test 'something that needs versioning' do
  with_versioning do
    expected_csv = File.open(file_fixture('sample.csv')).read

    assert_equal expected_csv
  end
end

I don't know how to get this newly created CSV file from a service.call so that I can compare it with expected_data inside assert_equal.

CodePudding user response：

Your service (I assume the service is CsvLogGenerator itself returns a string, so your test should read something like this (except I have omitted the apparently irrelevant with_versioning wrapper block)

class CsvLogGeneratorTest < ActiveSupport::TestCase
  setup do
    Book.create!(title: 'title')
  end

  test 'something that needs versioning' do
    service = CsvLogGenerator.new
    actual_csv = service.call
    expected_csv = File.open(file_fixture('sample.csv')).read

    assert_equal expected_csv, actual_csv
  end
end