“undefined method `env’ for nil:NilClass” in ‘setup_controller_for_warden’ error when testing Devise using Rspec

In Rails 5 you must include Devise::Test::IntegrationHelpers instead Devise::Test::ControllerHelpers:

# rails_helper.rb
config.include Devise::Test::IntegrationHelpers, type: :feature

See more:

• https://github.com/plataformatec/devise/issues/3913#issuecomment
• https://github.com/plataformatec/devise/pull/4071