Use expect for admin/ controllers (#33686)

spec/requests/admin/accounts_spec.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin Accounts' do
+  describe 'POST /admin/accounts/batch' do
+    before { sign_in Fabricate(:admin_user) }
+
+    it 'gracefully handles invalid nested params' do
+      post batch_admin_accounts_path(form_account_batch: 'invalid')
+
+      expect(response)
+        .to redirect_to(admin_accounts_path)
+    end
+  end
+end