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Adding Tests (Part 1)

At this point we have a working application. Before we continue addinging functionality, we need to add some tests to ensure that our application is working as expected.

Rails uses Minitest to run tests by default. Minitest is a framework that allows you to write tests in Ruby. Some applications will use Rspec, which is a Ruby testing framework that is similar to Minitest.

For this tutorial, we will use Minitest as it is the default Rails testing framework.

We actually have a bunch of tests already! When we started building the application we used some bin/rails generate commands to create some files, which included some tests by default.

Let's start by running bin/rails test to run the tests and see what is and isn't working.

Note: bin/rails test is a Rails command that runs all the tests in the test directory. If you want to run a specific test, you can use bin/rails test <path>. And you can run a specific test in that file by appending a colon and line number to the method definition: bin/rails test <path>:<lineno>.

Rexml

This may or may not happen depending on when you run through this tutorial.

In Ruby 3.0, there is a new gem called Rexml. This gem handles XML. Prior to Ruby 3.0, rexml was in the standard Ruby Library so a dependency of Rails (Selenium) did not need to manually include it.

Selenium is a testing framework that allows you to write integrations tests for web applications. It is a wrapper around the browser and allows you to interact with a running test-managed version of the web application in the test process.

You'll know you need to do this because you get an error message when you try to run the tests:

[...]/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/bootsnap-1.8.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:34:in `require': cannot load such file -- rexml/document (LoadError)

How do we fix this? Selenium has a fix for this, but it is not released yet and won't be for version 3.x. We need to use the beta version of Selenium.

In the group :test block, add gem 'rexml':

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 3.26'
  gem 'selenium-webdriver', '~> 4.0.0.beta4'
  # Easy installation and use of web drivers to run system tests with browsers
  gem 'webdrivers'
end

Now, we can't run just bundle install as we are updating a gem, so we need to run bundle update selenium-webdriver to update the specific gem. DO NOT RUN bundle update as it will update all the gems, which could be disastrous in an already deployed application as many things could break with dozens of version updates.

Tests should now start!

Fixtures

Fixtures are the default Rails way to inject information into the database so there are instances of all the various objects that we need to test.

Rails uses a special directory called test/fixtures to store the fixtures in YAML files. These YAML files are then loaded into the database as SQL. This is an important distinction as the objects in the fixture files will not run any ActiveRecord callbacks on creation.

Right now, our fixtures are failing to be loaded. We added some changes to the user model's email column, and the default value of MyString is invalid as it is not unique.

Error:
ChannelsControllerTest#test_should_destroy_channel:
Mysql2::Error: Duplicate entry 'MyString' for key 'index_users_on_email'

Let's open test/fixtures/users.yml and change the emails to be unique. I used one@example.com and two@example.com

Devise

All of our tests were built without the knowledge of our user authentication system. However, we added a before_action to our ApplicationController to authenticate the user. All of our controller tests are failing because of this.

There's not a ton of information about this issue as the response is valid and Rails doesn't know about it. We know, however, that this is an issue because we see errors like this:

Failure:
UsersControllerTest#test_should_get_edit [~/test/controllers/users_controller_test.rb:33]:
Expected response to be a <2XX: success>, but was a <302: Found> redirect to <http://www.example.com/users/sign_in>
Response body: <html><body>You are being <a href="http://www.example.com/users/sign_in">redirected</a>.</body></html>

There is a whole section in Devise's README on this topic: https://github.com/heartcombo/devise#test-helpers

The gist is that we need to add include Devise::Test::IntegrationHelpers to all of our controller tests and integration tests.

In test/controllers/*_controller_test.rb add include Devise::Test::IntegrationHelpers to the top of the class:

require "test_helper"

class ChannelsControllerTest < ActionDispatch::IntegrationTest
  include Devise::Test::IntegrationHelpers
  ...
end

Next, we need to log into the application using the newly included helper: sign_in @user

Within the setup block in each controller test, let's add sign_in(something_that_makes_sense)

  # messages_controller_test.rb
  setup do
    @message = messages(:one)
    sign_in(@message.sender)
  end
  # channels_controller_test.rb
  setup do
    @channel = channels(:one)
    sign_in(@channel.creator)
  end
  # users_controller_test.rb
  setup do
    @user = users(:one)
    sign_in(@user)
  end

Let's run the tests again and see if they work.

Wall of output

Right now if we run tests we will see a wall of errors, particularly ones like NameError: undefined local variable or method 'new_message_url'. This is because we changed the nesting of some of the models. If we run a single controller for a model that we didn't nest, we can see it works a bit better. So let's start there:

bin/rails test test/controllers/users_controller_test.rb

We have 2 failures. Let's focus on each individually.

UsersControllerTest#test_should_create_user

Failure:
UsersControllerTest#test_should_create_user [~/src/github.com/dcsil/chat_app/test/controllers/users_controller_test.rb:21]:
"User.count" didn't change by 1.
Expected: 3
  Actual: 2


rails test test/controllers/users_controller_test.rb:20

In this case we can see that we expected a new user to be created, but it wasn't. To fix this, I'd throw a debugger into the controller and see what the problem is.

  def create
    @user = User.new(user_params)
    debugger

Then I would rerun the test: rails test test/controllers/users_controller_test.rb:20

In this case, we are still failing AND we aren't hitting the debugger statement. What's going on?

Remember how we added devise? Devise handles registrations itself, so we have a conflicting route.

$ bin/rails routes --grep user
...
POST   /users(.:format)               devise/registrations#create
POST   /users(.:format)               users#create

The solution here is to remove the create action and associated tests.

In config/routes.rb, change resources :users to resources :users, except: [:create]

In app/controllers/user_controller.rb, remove the create action.

In test/controllers/users_controller_test.rb, remove the create test.

Great, now let's run user tests again.

bin/rails test test/controllers/users_controller_test.rb. Our only failure is now UsersControllerTest#test_should_destroy_user

UsersControllerTest#test_should_destroy_user

Error:
UsersControllerTest#test_should_destroy_user:
ActiveRecord::InvalidForeignKey: Mysql2::Error: Cannot delete or update a parent row: a foreign key constraint fails (`chat_app_test-0`.`memberships`, CONSTRAINT `fk_rails_99326fb65d` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`))
    app/controllers/users_controller.rb:53:in `destroy'
    test/controllers/users_controller_test.rb:45:in `block (2 levels) in <class:UsersControllerTest>'
    test/controllers/users_controller_test.rb:44:in `block in <class:UsersControllerTest>'


rails test test/controllers/users_controller_test.rb:35

This error is because we have a foreign key constraint. When we delete a user, we end up with a bunch of violated foreign keys in other tables like memberships.

We have a few options here:

  • Change the foreign key to allow nil (could be useful for channel creator)
  • Cascade destroy all associated objects
  • Change the user to be soft deleted

Let's use a mixture to fix this. A user, essentially, has a few associated objects:

  • Memberships
  • Messages
  • Created Channels

We don't want to treat these equally - for example we don't want a whole channel to go away when a user goes away, but we don't care about the user's memberships.

  • For memberships, we can add dependent: :destroy to the has_many :memberships in app/models/user.rb
  • For channels we can add dependent: :nullify to the has_many :channels in app/models/user.rb
    • We also need to change the database underneath this column.
    • Create a migration with bin/rails g migration NAME
    • In the migration change method, add: 
      def change
  remove_foreign_key :channels, :users
  change_column :channels, :user_id, :bigint, null: true
end
    • Migrate with bin/rails db:migrate
    • Finally, in channels.rb add optional: true to the belongs_to :creator line

All user conrroller tests now pass.

$ bin/rails test test/controllers/users_controller_test.rb
Running via Spring preloader in process 30512
Run options: --seed 18902

# Running:

......

Finished in 16.897910s, 0.3551 runs/s, 0.4143 assertions/s.
6 runs, 7 assertions, 0 failures, 0 errors, 0 skips

Let's take a break at this point :)

Action Items

  1. Change gem 'selenium-webdriver' in the Gemfile to gem 'selenium-webdriver', '~> 4.0.0.beta4' and run bundle update selenium-webdriver
  2. Open test/fixtures/users.yml and change emails to be unique
  3. Add include Devise::Test::IntegrationHelpers to all of our controller tests and integration tests.
  4. In the setup method in each of these test files, add sign_in(@user) where @user is replaced with something that makes sense for that file. E.g. @channel.creator for channels controller or @message.sender for messages controller.
  5. In config/routes.rb, change resources :users to resources :users, except: [:create]
  6. In app/controllers/user_controller.rb, remove the create action.
  7. In test/controllers/users_controller_test.rb, remove the create test.
  8. In app/models/user.rb, change the memberships line to has_many :memberships, dependent: :destroy
  9. In app/models/user.rb, change the channels line to has_many :channels, dependent: :nullify
  10. Run bin/rails g migration RemoveForeignKeyAndNullConstraintFromChannels
  11. Open the migration and change the method to: 
    def change
  remove_foreign_key :channels, :users
  change_column :channels, :user_id, :bigint, null: true
end
  12. Run bin/rails db:migrate
  13. Open app/models/channel.rb and add optional: true to the belongs_to :creator line
  14. Done! bin/rails test test/controllers/users_controller_test.rb should now pass.

This section in the example app

https://github.com/dcsil/rails-tutorial-example/commit/69c6d1eb57e2cb2c748a5cdc3fe5582bdd0bd735

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