Add coverage for misc serializers (#32781)

spec/serializers/rest/account_warning_serializer_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe REST::AccountWarningSerializer do
+  subject { serialized_record_json(record, described_class) }
+
+  let(:record) { Fabricate :account_warning, id: 123, status_ids: [456, 789] }
+
+  describe 'serialization' do
+    it 'returns expected values' do
+      expect(subject)
+        .to include(
+          'id' => be_a(String).and(eq('123')),
+          'status_ids' => be_a(Array).and(eq(['456', '789']))
+        )
+    end
+  end
+end