rails-controller-testing Gem

I just pulled my app up to edge rails. I've fixed most compatibility issues, however tests are now giving errors like this:

NoMethodError: assigns has been extracted to a gem. To continue using it,
    add `gem 'rails-controller-testing'` to your Gemfile.

The first time this occurred, I added gem 'rails-controller-testing' to my Gemfile in the :test group and ran bundle. According to this process, the gem is now installed, however I am getting the same errors. How do I resolve them?