Add coverage for misc serializers (#32781)

spec/serializers/rest/admin/account_serializer_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe REST::Admin::AccountSerializer do
+  subject { serialized_record_json(record, described_class) }
+
+  describe 'created_by_application_id' do
+    context 'when account is application-created' do
+      let(:record) { Fabricate :account, user: Fabricate(:user, created_by_application: application) }
+      let(:application) { Fabricate :application }
+
+      it { is_expected.to include('created_by_application_id' => application.id.to_s) }
+    end
+  end
+
+  describe 'invited_by_account_id' do
+    context 'when account was invited' do
+      let(:record) { Fabricate :account, user: Fabricate(:user, invite: invite) }
+      let(:invite) { Fabricate :invite }
+
+      it { is_expected.to include('invited_by_account_id' => invite.user.account.id.to_s) }
+    end
+  end
+end