Error in cancancan ability initializer when testing controllers - ruby-on-rails

Question

I added cancancan gem to my app, but it broked all my controller and feature tests. The error start in ability.rb initialize: the user variable is nil.
Here is the error log of one of the tests:
14) TestCasesController DELETE #destroy when not logged-in redirects to sign-in page
Failure/Error: if user.teacher?
NoMethodError:
undefined method `teacher?' for nil:NilClass
# ./app/models/ability.rb:5:in `initialize'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_additions.rb:361:in `new'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_additions.rb:361:in `current_ability'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_additions.rb:342:in `authorize!'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_resource.rb:49:in `authorize_resource'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_resource.rb:34:in `load_and_authorize_resource'
# /usr/local/rvm/gems/ruby-2.3.1/gems/cancancan-1.15.0/lib/cancan/controller_resource.rb:10:in `block in add_before_action'
# /usr/local/rvm/gems/ruby-2.3.1/gems/rails-controller-testing-1.0.1/lib/rails/controller/testing/template_assertions.rb:61:in `process'
# /usr/local/rvm/gems/ruby-2.3.1/gems/devise-4.2.0/lib/devise/test/controller_helpers.rb:33:in `block in process'
# /usr/local/rvm/gems/ruby-2.3.1/gems/devise-4.2.0/lib/devise/test/controller_helpers.rb:100:in `catch'
# /usr/local/rvm/gems/ruby-2.3.1/gems/devise-4.2.0/lib/devise/test/controller_helpers.rb:100:in `_catch_warden'
# /usr/local/rvm/gems/ruby-2.3.1/gems/devise-4.2.0/lib/devise/test/controller_helpers.rb:33:in `process'
# /usr/local/rvm/gems/ruby-2.3.1/gems/rails-controller-testing-1.0.1/lib/rails/controller/testing/integration.rb:12:in `block (2 levels) in <module:Integration>'
# ./spec/controllers/test_cases_controller_spec.rb:182:in `block (3 levels) in <top (required)>'
# ./spec/controllers/test_cases_controller_spec.rb:193:in `block (4 levels) in <top (required)>'
Here is the corresponding action:
describe "DELETE #destroy" do
let!(:test_case) { create(:test_case) }
subject { delete :destroy, params: { id: test_case } }
context "when not logged-in" do
before { subject }
it "redirects to sign-in page" do
expect(response).to redirect_to(new_user_session_url)
end
end
end
This is my controller:
class TestCasesController < ApplicationController
include ApplicationHelper
load_and_authorize_resource
before_action :authenticate_user!
before_action :find_test_case, only: [:show, :edit, :update, :destroy, :test]
before_action :find_question, only: [:index, :new, :create, :test_all]
def index
#test_cases = TestCase.where(question: #question)
end
def new
#test_case = TestCase.new
end
def create
#test_case = #question.test_cases.build(test_case_params)
if #test_case.save
flash[:success] = "Caso de teste criado!"
redirect_to #test_case
else
render 'new'
end
end
def show
end
def edit
end
def update
if #test_case.update_attributes(test_case_params)
flash[:success] = "Caso de teste atualizado!"
redirect_to #test_case
else
render 'edit'
end
end
def destroy
question = #test_case.question
#test_case.destroy
flash[:success] = "Caso de teste deletado!"
redirect_to question_test_cases_url(question)
end
def test
result = #test_case.test(plain_current_datetime, "pas", params[:source_code])
#output = result[:output]
#results = [ { title: #test_case.title, status: result[:status] } ]
respond_to { |format| format.js }
end
def test_all
#results = #question.test_all(plain_current_datetime, "pas", params[:source_code])
respond_to { |format| format.js }
end
private
def test_case_params
params.require(:test_case).permit(:title, :description, :input, :output, :question_id)
end
def find_test_case
#test_case = TestCase.find(params[:id])
end
def find_question
#question = Question.find(params[:question_id])
end
end
This is my ability class:
class Ability
include CanCan::Ability
def initialize(user)
if user.teacher?
can :manage, [Exercise, Question, TestCase]
can :manage, Team, owner: user
can [:read, :create], Team
can [:enroll], Team do |team|
!team.enrolled?(user)
end
can [:unenroll], Team do |team|
team.enrolled?(user)
end
end
end
end
This is my rails_helper (from rspec):
# This file is copied to spec/ when you run 'rails generate rspec:install'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
# Prevent database truncation if the environment is production
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'spec_helper'
require 'rspec/rails'
# Add additional requires below this line. Rails is not loaded until this point!
require 'support/helpers/relationships'
# Requires supporting ruby files with custom matchers and macros, etc, in
# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
# run as spec files by default. This means that files in spec/support that end
# in _spec.rb will both be required and run as specs, causing the specs to be
# run twice. It is recommended that you do not name files matching this glob to
# end with _spec.rb. You can configure this pattern with the --pattern
# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
#
# The following line is provided for convenience purposes. It has the downside
# of increasing the boot-up time by auto-requiring all files in the support
# directory. Alternatively, in the individual `*_spec.rb` files, manually
# require only the support files necessary.
#
# Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }
# Checks for pending migration and applies them before tests are run.
# If you are not using ActiveRecord, you can remove this line.
ActiveRecord::Migration.maintain_test_schema!
RSpec.configure do |config|
# Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
config.fixture_path = "#{::Rails.root}/spec/fixtures"
# If you're not using ActiveRecord, or you'd prefer not to run each of your
# examples within a transaction, remove the following line or assign false
# instead of true.
config.use_transactional_fixtures = true
# RSpec Rails can automatically mix in different behaviours to your tests
# based on their file location, for example enabling you to call `get` and
# `post` in specs under `spec/controllers`.
#
# You can disable this behaviour by removing the line below, and instead
# explicitly tag your specs with their type, e.g.:
#
# RSpec.describe UsersController, :type => :controller do
# # ...
# end
#
# The different available types are documented in the features, such as in
# https://relishapp.com/rspec/rspec-rails/docs
config.infer_spec_type_from_file_location!
# Helpers
config.include Helpers::Relationships, type: :model
config.include Devise::Test::ControllerHelpers, :type => :controller
config.include Warden::Test::Helpers
end
Any tips of how to fix that?
OBS: I'm using Devise for authentication, it provides me the required current_user to cancancan work.

Answer 1

The primary reason you're getting a nil:NilClass error is because current_user is nil unless you are signed in via Devise. Your ability needs to handle for when a user is not logged in, something like this:
def initialize(user)
return unless user.present?
if user.teacher?
...
end
end
If you return nil from your ability, the authorization fails and is handled accordingly.