Add test for post-migration scheduling

db/post_migrate/20220204194347_encrypt_integration_properties.rb

@@ -3,13 +3,18 @@
 class EncryptIntegrationProperties < Gitlab::Database::Migration[1.0]
   disable_ddl_transaction!
   MIGRATION = 'EncryptIntegrationProperties'
+  BATCH_SIZE = 5_000
+  INTERVAL = 2.minutes.to_i
 
   def up
+    requiring_update = define_batchable_model('integrations').where.not(properties: nil)
+
     queue_background_migration_jobs_by_range_at_intervals(
-      define_batchable_model('integrations').where.not(properties: nil),
+      requiring_update,
       MIGRATION,
-      2.minutes.to_i,
-      track_jobs: true
+      INTERVAL,
+      track_jobs: true,
+      batch_size: BATCH_SIZE
     )
   end
 

spec/migrations/20220204194347_encrypt_integration_properties_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+require_migration!
+
+RSpec.describe EncryptIntegrationProperties, :migration, schema: 20220204193000 do
+  subject(:migration) { described_class.new }
+
+  let(:integrations) { table(:integrations) }
+
+  before do
+    stub_const("#{described_class.name}::BATCH_SIZE", 2)
+  end
+
+  it 'correctly schedules background migrations', :aggregate_failures do
+    # update required
+    record1 = integrations.create!(properties: some_props)
+    record2 = integrations.create!(properties: some_props)
+    record3 = integrations.create!(properties: some_props)
+
+    # no update required
+    integrations.create!(properties: nil)
+
+    Sidekiq::Testing.fake! do
+      freeze_time do
+        migrate!
+
+        expect(described_class::MIGRATION).to be_scheduled_migration(record1.id, record2.id)
+        expect(described_class::MIGRATION).to be_scheduled_migration(record3.id, record3.id)
+
+        expect(BackgroundMigrationWorker.jobs.size).to eq(2)
+      end
+    end
+  end
+
+  def some_props
+    { iid: generate(:iid), url: generate(:url), username: generate(:username) }.to_json
+  end
+end