Add caching for payload serialization during fan-out (#19642)

spec/lib/status_cache_hydrator_spec.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe StatusCacheHydrator do
+  let(:status)  { Fabricate(:status) }
+  let(:account) { Fabricate(:account) }
+
+  describe '#hydrate' do
+    subject { described_class.new(status).hydrate(account.id) }
+
+    let(:compare_to_hash) { InlineRenderer.render(status, account, :status) }
+
+    context 'when cache is warm' do
+      before do
+        Rails.cache.write("fan-out/#{status.id}", InlineRenderer.render(status, nil, :status))
+      end
+
+      it 'renders the same attributes as a full render' do
+        expect(subject).to include(compare_to_hash)
+      end
+    end
+
+    context 'when cache is cold' do
+      before do
+        Rails.cache.delete("fan-out/#{status.id}")
+      end
+
+      it 'renders the same attributes as a full render' do
+        expect(subject).to include(compare_to_hash)
+      end
+    end
+
+    context 'when account has favourited status' do
+      before do
+        FavouriteService.new.call(account, status)
+      end
+
+      it 'renders the same attributes as a full render' do
+        expect(subject).to include(compare_to_hash)
+      end
+    end
+
+    context 'when account has reblogged status' do
+      before do
+        ReblogService.new.call(account, status)
+      end
+
+      it 'renders the same attributes as a full render' do
+        expect(subject).to include(compare_to_hash)
+      end
+    end
+  end
+end