Fix empty authors preview card serialization (#33151)

spec/serializers/rest/preview_card_serializer_spec.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe REST::PreviewCardSerializer do
+  subject do
+    serialized_record_json(
+      preview_card,
+      described_class
+    )
+  end
+
+  context 'when preview card does not have author data' do
+    let(:preview_card) { Fabricate.build :preview_card }
+
+    it 'includes empty authors array' do
+      expect(subject.deep_symbolize_keys)
+        .to include(
+          authors: be_an(Array).and(be_empty)
+        )
+    end
+  end
+
+  context 'when preview card has author data' do
+    let(:preview_card) { Fabricate.build :preview_card, author_name: 'Name', author_url: 'https://host.example/123' }
+
+    it 'includes populated authors array' do
+      expect(subject.deep_symbolize_keys)
+        .to include(
+          authors: be_an(Array).and(
+            contain_exactly(
+              include(
+                name: 'Name',
+                url: 'https://host.example/123'
+              )
+            )
+          )
+        )
+    end
+  end
+end