add specs for migration

spec/factories/report_rendering_options_factory.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :orders_and_distributors_options, class: ReportRenderingOptions do
+    report_type { "orders_and_distributors" }
+  end
+end

spec/migrations/20241011071014_update_item_name_to_product_in_od_report_spec.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require_relative '../../db/migrate/20241011071014_update_item_name_to_product_in_od_report'
+
+RSpec.describe UpdateItemNameToProductInODReport, type: :migration do
+  let!(:report_option_without_item_name_product) do
+    create(
+      :orders_and_distributors_options,
+      options: { fields_to_show: ['other_field'] }
+    )
+  end
+
+  describe '#up' do
+    let!(:report_option_with_item_name) do
+      create(
+        :orders_and_distributors_options,
+        options: { fields_to_show: ['item_name', 'other_field'] }
+      )
+    end
+    before { subject.up }
+
+    it 'updates fields_to_show from item_name to product only if options have item_name' do
+      report_option_with_item_name.reload
+      expect(fields_to_show(report_option_with_item_name)).to eq(['other_field', 'product'])
+      expect(fields_to_show(report_option_without_item_name_product)).to eq(['other_field'])
+    end
+  end
+
+  describe '#down' do
+    let!(:report_option_with_product) do
+      create(
+        :orders_and_distributors_options,
+        options: { fields_to_show: ['product', 'other_field'] }
+      )
+    end
+    before { subject.down }
+
+    it 'reverts fields_to_show from product to item_name only if options have product' do
+      report_option_with_product.reload
+      expect(fields_to_show(report_option_with_product)).to eq(['other_field', 'item_name'])
+      expect(fields_to_show(report_option_without_item_name_product)).to eq(['other_field'])
+    end
+  end
+
+  def fields_to_show(report_options)
+    report_options.options[:fields_to_show]
+  end
+end