Test a model in Rails 5 using Rspec in 3 steps

I create a basic Rails 5 application, add an scaffold and create some basic tests on the model. I use RSpec for the test environment, Factory Girl for the factories and Faker to generate some test data. Ready? Let’s go!.

Step 1. Prepare the basic infrastructure

I’am using RVM to keep the Rails’ versions under control, but you can use other tool to do it; the important thing here is to choose Rails 5 in your environment.

So I create the app as usual.

	$ rvm list
	rvm rubies
	ruby-1.9.3-p484 [ x86_64 ]
	ruby-2.1.0 [ x86_64 ]
	ruby-2.2.0 [ x86_64 ]
	ruby-2.2.2 [ x86_64 ]
	=* ruby-2.3.0 [ x86_64 ]
	# => - current
	# =* - current && default
	# * - default
	$ rails new basic_rspec

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Then I can add the corresponding gems to Gemfile:

	...
	group :development, :test do
	gem 'rspec-rails'
	gem 'rails-controller-testing'
	gem 'factory_girl_rails'
	gem 'faker'
	# Call 'byebug' anywhere in the code to stop execution and get a debugger console
	gem 'byebug', platform: :mri
	end
	...

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The next step is to install the gems, generate the basic RSpec infrastructure and create the scaffold for our Person class, the class I will use as example:

	$ bundle install
	Resolving dependencies...
	Using rake 12.0.0
	Using concurrent-ruby 1.0.2
	Using i18n 0.7.0
	...
	(more gems here...)
	...
	Using web-console 3.4.0
	Using rails 5.0.0.1
	Using sass-rails 5.0.6
	Bundle complete! 19 Gemfile dependencies, 72 gems now installed.
	Use `bundle show [gemname]` to see where a bundled gem is installed.
	$ rails generate rspec:install
	Running via Spring preloader in process 4039
	Expected string default value for '--jbuilder'; got true (boolean)
	create .rspec
	create spec
	create spec/spec_helper.rb
	create spec/rails_helper.rb
	$ rails generate scaffold Person name:string age:integer
	Running via Spring preloader in process 4046
	Expected string default value for '--jbuilder'; got true (boolean)
	invoke active_record
	create db/migrate/20161207175605_create_people.rb
	create app/models/person.rb
	invoke rspec
	create spec/models/person_spec.rb
	invoke factory_girl
	create spec/factories/people.rb
	invoke resource_route
	route resources :people
	invoke scaffold_controller
	create app/controllers/people_controller.rb
	invoke erb
	create app/views/people
	create app/views/people/index.html.erb
	create app/views/people/edit.html.erb
	create app/views/people/show.html.erb
	create app/views/people/new.html.erb
	create app/views/people/_form.html.erb
	invoke rspec
	create spec/controllers/people_controller_spec.rb
	create spec/views/people/edit.html.erb_spec.rb
	create spec/views/people/index.html.erb_spec.rb
	create spec/views/people/new.html.erb_spec.rb
	create spec/views/people/show.html.erb_spec.rb
	create spec/routing/people_routing_spec.rb
	invoke rspec
	create spec/requests/people_spec.rb
	invoke helper
	create app/helpers/people_helper.rb
	invoke rspec
	create spec/helpers/people_helper_spec.rb
	invoke jbuilder
	create app/views/people/index.json.jbuilder
	create app/views/people/show.json.jbuilder
	create app/views/people/_person.json.jbuilder
	invoke assets
	invoke coffee
	create app/assets/javascripts/people.coffee
	invoke scss
	create app/assets/stylesheets/people.scss
	invoke scss
	create app/assets/stylesheets/scaffolds.scss

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I edit the model in order to add two validations and a new method ‘identifier’ that returns a concatenated string. The validations and the method will be used later on the tests.

	# app/models/person.rb
	Person < ApplicationRecord
	validates :name, presence: true
	validates :age, presence: true
	def identifier
	[name, age].join " "
	end
	end

view raw person.rb hosted with by GitHub

With this in place I migrate the database and prepare the tests. At this point I should be able to execute the test created by the scaffold (31 in total in this case).

	$ rake db:migrate
	== 20161207175605 CreatePeople: migrating =====================================
	-- create_table(:people)
	-> 0.0010s
	== 20161207175605 CreatePeople: migrated (0.0010s) ============================
	$ rake db:test:prepare
	$ rspec
	...
	Finished in 1.58 seconds (files took 1.64 seconds to load)
	31 examples, 0 failures, 17 pending

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Step 2. Add the factories

Add the factories to create valid objects to be used in the tests. To do so create the ‘people.rb’ file (note the file name ‘people’, plural of ‘person’). I also include Faker to generate fake values on the object’s attributes.

	# spec/factories/people.rb
	require 'faker'
	FactoryGirl.define do
	factory :person do
	name { Faker::Name.first_name }
	age { Faker::Number.between(0, 100) }
	end
	end

view raw people.rb hosted with by GitHub

Step 3. Add the tests

I will verify the Person class has a valid factory, that it is not valid without a name and an age, and that the ‘identifier’ method returns a valid value. This shouldn’t be difficult.

	# spec/models/person_spec.rb
	require 'rails_helper'
	RSpec.describe Person, type: :model do
	it "has a valid factory" do
	#person = FactoryGirl.build(:person) it is also valid
	expect(FactoryGirl.build(:person)).to be_valid
	end
	it "is invalid without a name" do
	person = FactoryGirl.build(:person, name: nil)
	expect(person).not_to be_valid
	end
	it "is invalid without an age" do
	person = FactoryGirl.build(:person, age: nil)
	expect(person).not_to be_valid
	end
	it "returns a person's identifier as a string" do
	person = FactoryGirl.build(:person, name: "Johnny", age: 12)
	expect(person.identifier).to eq("Johnny 12")
	end
	end

view raw person_spec.rb hosted with by GitHub

Et voila! I can easily execute the test… with 0 failures!!

	$ rspec spec/models/person_spec.rb
	...
	Finished in 0.39298 seconds (files took 2.32 seconds to load)
	4 examples, 0 failures

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