Add retention policy for cached content and media (#19232)

spec/lib/vacuum/preview_cards_vacuum_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+RSpec.describe Vacuum::PreviewCardsVacuum do
+  let(:retention_period) { 7.days }
+
+  subject { described_class.new(retention_period) }
+
+  describe '#perform' do
+    let!(:orphaned_preview_card) { Fabricate(:preview_card, created_at: 2.days.ago) }
+    let!(:old_preview_card) { Fabricate(:preview_card, updated_at: (retention_period + 1.day).ago) }
+    let!(:new_preview_card) { Fabricate(:preview_card) }
+
+    before do
+      old_preview_card.statuses << Fabricate(:status)
+      new_preview_card.statuses << Fabricate(:status)
+
+      subject.perform
+    end
+
+    it 'deletes cache of preview cards last updated before the retention period' do
+      expect(old_preview_card.reload.image).to be_blank
+    end
+
+    it 'does not delete cache of preview cards last updated within the retention period' do
+      expect(new_preview_card.reload.image).to_not be_blank
+    end
+
+    it 'does not delete attached preview cards' do
+      expect(new_preview_card.reload).to be_persisted
+    end
+
+    it 'deletes preview cards not attached to any status' do
+      expect { orphaned_preview_card.reload }.to raise_error ActiveRecord::RecordNotFound
+    end
+  end
+end