Use expect in Admin::ExportControllerConcern import params (#33745)

spec/requests/admin/export_domain_blocks_spec.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin Export Domain Blocks' do
+  describe 'POST /admin/export_domain_blocks/import' do
+    before { sign_in Fabricate(:admin_user) }
+
+    it 'gracefully handles invalid nested params' do
+      post import_admin_export_domain_blocks_path(admin_import: 'invalid')
+
+      expect(response.body)
+        .to include(I18n.t('admin.export_domain_blocks.no_file'))
+    end
+  end
+end