An in-depth look at unit testing Rails models with RSpec with TDD.

This episode covers:

  • Creating a Console model (0:45)
  • Testing model validations (3:28)
  • Testing model methods (12:17)
  • Testing model scopes (15:12)
  • Refactoring the consoles array of hashes into database queries (20:12)

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Key code from the episode:

# db/migrate/20171111171300_create_consoles.rb class CreateConsoles < ActiveRecord::Migration[5.1] def change create_table :consoles do |t| t.string :name, null: false t.string :manufacturer, null: false t.timestamps end end end 
# app/models/console.rb class Console < ActiveRecord::Base validates :name, presence: true validates :manufacturer, presence: true scope :nintendo, -> { where(manufacturer: 'Nintendo') } def formatted_name "#{manufacturer} #{name}" end end 
# spec/models/console_spec.rb require 'rails_helper' RSpec.describe Console do subject { described_class.new(manufacturer: 'Nintendo', name: 'Wii') } describe 'validations' do describe 'name' do it 'must be present' do expect(subject).to be_valid subject.name = nil expect(subject).to_not be_valid end end describe 'manufacturer' do it 'must be present' do expect(subject).to be_valid subject.manufacturer = nil expect(subject).to_not be_valid end end end describe '#formatted_name' do it 'returns the manufacturer and name in a string' do expect(subject.formatted_name).to eql('Nintendo Wii') end end describe '.nintendo' do it 'returns an ActiveRecord::Relation of consoles manufacturered by Nintendo' do wii = described_class.create(manufacturer: 'Nintendo', name: 'Wii') switch = described_class.create(manufacturer: 'Nintendo', name: 'Switch') described_class.create(manufacturer: 'Sony', name: 'PS4') expect(described_class.nintendo).to contain_exactly( wii, switch ) end end end 
# app/controllers/consoles_controller.rb class ConsolesController < ApplicationController def index if params[:manufacturer].present? consoles = Console.where(manufacturer: params[:manufacturer]) else consoles = Console.all end render(json: { 'consoles' => consoles.map(&:formatted_name) }) end end 
# spec/requests/consoles_spec.rb require 'rails_helper' RSpec.describe 'Consoles requests' do before do Console.create(name: 'NES', manufacturer: 'Nintendo') Console.create(name: 'SNES', manufacturer: 'Nintendo') Console.create(name: 'Wii', manufacturer: 'Nintendo') Console.create(name: 'Genesis', manufacturer: 'Sega') Console.create(name: 'Xbox', manufacturer: 'Microsoft') Console.create(name: 'Switch', manufacturer: 'Nintendo') Console.create(name: 'PS1', manufacturer: 'Sony') Console.create(name: 'PS2', manufacturer: 'Sony') end describe 'GET /consoles' do it 'returns an array of the consoles' do get('/consoles') expect(response_json['consoles']).to contain_exactly( 'Nintendo NES', 'Nintendo SNES', 'Nintendo Wii', 'Sega Genesis', 'Microsoft Xbox', 'Nintendo Switch', 'Sony PS1', 'Sony PS2' ) end it 'supports specifying consoles for a specific manufacturer' do get('/consoles', params: { manufacturer: 'Nintendo' }) expect(response_json['consoles']).to contain_exactly( 'Nintendo NES', 'Nintendo SNES', 'Nintendo Wii', 'Nintendo Switch' ) end end end

Software used:

  • Ruby 2.4.2
  • RSpec 3.6.1
  • Rails 5.1.4
  • Mac OS
  • iTerm 2
  • Vim
  • Tmux