[Ruby on Rails] Model test with RSpec

Development environment

ruby 2.5.7 Rails OS: macOS Catalina


[Ruby on Rails] Until RSpec is introduced We will proceed on the premise that this is done.

model test preparation

・ Validation settings

This time we will test if there is a title column and the number of characters.


class Post < ApplicationRecord
  belongs_to :user
  validates :title, presence: true, length: {maximum: 20}

・ Creating a file

① Create models folder and factories folder under spec, Also create a file for the model you want to test. This time we will test the post model. Also, to ensure that users can only post while logged in, Also create a use model. The file structure is as follows.   spec/models/post_spec.rb → Describe what you want to test

spec/factories/post.rb spec/factories/user.rb → Create dummy data

② Enables Factory Bot. It is convenient to use it because you can register the DB and build the model like user = create (: user). Create a support folder and factory_bot.rb file under spec and describe as follows.


RSpec.configure do |config|
  config.include FactoryBot::Syntax::Methods

Then add the following:


# This file is copied to spec/ when you run 'rails generate rspec:install'
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../config/environment', __dir__)
# Prevent database truncation if the environment is production
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'
require 'support/factory_bot' #<-Addition


Actual code

First, create dummy data.


FactoryBot.define do
  factory :user do
    email { Faker::Internet.email }
    phone_number { 12345678909 }
    password { 'password' }
    password_confirmation { 'password' }


FactoryBot.define do
  factory :post do
    body { Faker::Lorem.characters(number:20) }

Next, write the test code.


require 'rails_helper'

RSpec.describe 'Post model testing', type: :model do
  describe 'Validation test' do
    #Use the dummy data created by factories.
    let(:user) { FactoryBot.create(:user) }
    let!(:post) { build(:post, user_id: user.id) }

    # test_Create a post and check if you can register in the blank.
    subject { test_post.valid? }
    let(:test_post) { post }

    context 'title column' do
      it 'Must not be blank' do
        test_post.title = ''
        is_expected.to eq false;
      it 'Must be 20 characters or less' do
        post.title = Faker::Lorem.characters(number:21)
        expect(post.valid?).to eq false;
  describe 'Testing the association' do
    context 'Relationship with customer model' do
      it 'N:Is 1' do
        expect(Post.reflect_on_association(:user).macro).to eq :belongs_to

    # has_It is also described by many relationships.
    # context 'Relationship with PostComment model' do
      # it '1:Is N' do
        # expect(Post.reflect_on_association(:post_comments).macro).to eq :has_many
      # end
    # end

Then do the following in your terminal:

$ rspec spec/models

If you pass the test

Finished in 0.52408 seconds (files took 2.11 seconds to load)
3 examples, 0 failures

Since it is displayed like this, it means that the test content is correct.

On the contrary, if it does not pass the test, you can see where the error is occurring in this way, so You will be able to see if the test code is wrong, the validation is wrong, and so on.


  1)Post model test Validation test title column Must be 20 characters or less
     Failure/Error: let!(:post) { build(:post) }
       undefined method `build' for #<RSpec::ExampleGroups::Post::Nested::Title:0x000000000619e938>
     # ./spec/models/post_spec.rb:9:in `block (3 levels) in <top (required)>'

  2)Post model test Validation test title column Must not be blank
     Failure/Error: let!(:post) { build(:post) }
       undefined method `build' for #<RSpec::ExampleGroups::Post::Nested::Title:0x0000000007491518>
     # ./spec/models/post_spec.rb:9:in `block (3 levels) in <top (required)>'
Finished in 0.07992 seconds (files took 2.41 seconds to load)
2 examples, 2 failures

Failed examples:

rspec ./spec/models/post_spec.rb:11 #Post model test Validation test title column Must be 20 characters or less
rspec ./spec/models/post_spec.rb:15 #Post model test Validation test title column Must not be blank

Also, using rspec ./spec/models/post_spec.rb:11 at the bottom, You can also check the test contents individually as shown below.


$ rspec spec/models/post_spec.rb:11


This time 1, Validation to prevent registration with blank presence: true 2, Validation of character limit length: {maximum: 20} 3, Confirmation of relationship relationships belongs_to: user

I tested the above, but there are many other testing methods, so If you are interested, please check it out.

Also, on twitter, technologies and ideas that have not been uploaded to Qiita are also uploaded, so I would be grateful if you could follow me. Click here for details https://twitter.com/japwork

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