Rails test/unit testing helper method, NoMethodError: undefined method

Question

How to avoid this error:

Error: test_update_location(LocationControllerTest)
NoMethodError: undefined method `show_previous_version' for test_update_location(LocationControllerTest):LocationControllerTest/usr/local/rvm/gems/ruby-1.9.3-p327/gems/actionpack-2.1.1/lib/action_controller/test_process.rb:467:in `method_missing'

I want to test the helper method show_previous_version defined in app/helpers/description_helper.rb:

def show_previous_version(obj)
    ...
  return html
end

In app/helpers/application _helper.rb:

module ApplicationHelper
  .....
  require_dependency 'description_helper'
  ...
end

In test/functional/location_controller_test.rb

def test_update_location
  ...
  loc = Location.find(loc.id)
  html = show_previous_version(loc)
  ...
end

When I run the tests, I get:

Error: test_update_location(LocationControllerTest)
NoMethodError: undefined method `show_previous_version' for test_update_location(LocationControllerTest):LocationControllerTest/usr/local/rvm/gems/ruby-1.9.3-p327/gems/actionpack-2.1.1/lib/action_controller/test_process.rb:467:in `method_missing'

Answer 1

Helper methods are available to the controller instance, not on the test itself. Either include the helper directly in the test (messy), or use the controller (or some other object that includes the helper) to call that method.

To test using the controller, you can use the @controller instance variable inside an ActionController::TestCase:

class LocationControllerTest < ActionController::TestCase

  def test_update_location
    ...
    loc = Location.find(loc.id)
    html = @controller.show_previous_version(loc)
    ...
  end
end