Rails namespacing test gotchas

We have some controllers that are namespaced as Admin controllers eg: Admin::ProductController.

...and this is a legacy system, and never had any functional tests created for those...

So I was trying to get started on adding some functional tests. I created a test/functional/admin folder, then added a product_controller_test.rb under that, with the usual:

class ProductController < ActionController::TestCase

At first, the tests wouldn't even load properly, and I was getting the following error:

uninitialized constant ActionController (NameError)

That, apparently, is solved by explicitly putting:

require 'test_helper'

at the top of the file. After which it loads fine, and the null-test runs. but after that, I kept getting the following error:

RuntimeError: @controller is nil: make sure you set it in your test's setup method

It seems that you need to namespace your tests too, so instead of the class declaration I have above, you need:

class Admin::ProductController < ActionController::TestCase

The admin folder isn't enough.