Setting Up Your Rails App Test Suite with RSpec, Factory Girl, and Faker

Lately, I've been impressed with the importance of testing when writing an application. Writing tests forces you to slow down and really think about the code you want to write. Especially for beginners, it can be easy to start furiously typing at the keyboard, but that type of development lends itself to buggy, sloppy code.

Of course, I'm one to talk. When I'm pressed for time and just exploring a new concept, I tend to just start hacking away with little regard for the methods or models I need. But now that I've got a year of professional development under my belt, I think it's time to be more disciplined about my approach.

Thus, in my most recent side project, an app for tracking ice cream reviews, I've decided to write some tests! This isn't a purely TDD approach. I got to a point where it was getting harder for me to make sense of my code, so I decided to write some tests to cut down on my own confusion.

It's been quite some time since I set up my own suite, so the following is a guide for how to set up your Rails app's test suite with RSpec, Factory Girl, and Faker.

Install and Configure RSpec

RSpec is a testing framework for Ruby, and to integrate it with my Rails app, I used the rspec-rails gem. There are instructions in the documentation, but I'll paraphrase them here for ease of setting up everything all at once.

  1. Add rspec-rails to the :development and :test groups in your Gemfile.
  2. From your terminal, run bundle install
  3. Run rails generate rspec:install

This last step will add the following files to your app to configure RSpec: .rspec, spec/spec_helper.rb, spec/rails_helper.rb

Now, when you want to run the test suite, simply run bundle exec rspec from your terminal.

There are many types of specs you can write, including model, controller, mailer, and job. For each of these types of specs, I would place a new directory within the spec directory.

For example, my directory structure for model specs in my ice cream app would look something like this:

-- app
-- spec
  -- models
    -- flavor_spec.rb
    -- ice_cream_spec.rb
    -- user_spec.rb

To see the exact syntax for writing tests, I would check out the documentation on GitHub.

Here's an example of a simple test for my User model, though.

require "rails_helper"

describe User, type: :model do # This line describes what class you're
# testing
  describe "validations" do # Here I'm grouping all of my validations
 # together. 
    context "without an email" do # I'm using the context to specify the
    # exact condition
      it "is invalid without an email" do # This is a basic test block with
      # a description
        user = build(:user, email: nil) # This is where I set up the test
        # user that will be invalid. I'm using Factory Girl to generate the
        # test data and specifying the precise condition under which I expect
        # failure
        expect(user).to be_invalid # This line is just the expectation that
        # will return true or false, pass or fail

    context "when there are duplicate emails" do
      it "is invalid" do
        user = create(:user, email: "")
        invalid_user = build(:user, email: "")
        expect(invalid_user).to be_invalid


I'll cover more about Factory Girl next.

Set Up Factory Girl

Factory Girl is a library that makes it easy to set up test data in Ruby. Instead of using fixtures, you can use factories to generate dynamic objects on the fly, and Factory Girl is flexible enough so that you can also build stubs of objects instead of having to persist an object to the database, which can considerably slow down your test suite.

(And we all know that if the tests are slow, you're probably less inclined to write them at all.)

Okay, so one of the gotchas I encountered when trying to install Factory Girl was that instead of using the generic factory_girl gem, I actually had to use the factory_girl_rails gem to use it with Rails.

The steps after that are fairly straightfoward.

  1. Add factory_girl_rails to your Gemfile

group :development, :test do
  gem `factory_girl_rails`
  1. Run bundle install

Going forward, Rails should generate factories in the spec/factories directory.

  1. Now you'll need to do some configuration.

From the terminal, touch spec/support/factory_girl.rb In this file, write the following:

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

Now, require this file in the rails_helper with require 'support/factory_girl'

Remember: Each of your spec files should require 'rails_helper'

Setting up factories after the initial setup should be pretty easy, but I'll leave that until after we incorporate Faker, so we can get some more interesting test data.

Set Up Faker

Faker is great because it generates random data for you to use within your test suite (or, I suppose, within your seed data if you're just doing a demo app). It's open source, so you should totally contribute with more test data. Just for fun, they have Harry Potter and Star Wars-themed data...but in general, you should probably have test data that matches most closely the data you're expecting in your app.

Setup is easy.

Add the faker gem to your :development and :test groups in your Gemfile. Then bundle install.

You don't need to do much else beyond that besides consult the docs for which data is available and how to use it.

Setting Up a Factory with Factory Girl and Faker

By convention, you should write a separate factory for each domain model in your application. These will go in the spec/factories directory.

A basic factory is pretty easy to write.

FactoryGirl.define do
  factory :ice_cream, class: IceCream do
    title { Faker::Food.ingredient }    #This is where you define the
    # attributes
    image { Faker::LoremPixel.image  }  # You can write your own default
    # values, or pass a block in the curly braces for dynamic values
    parlor # This is for setting up an associated model

To use the factory in your test, you would write something like this:

ice_cream        = build(:ice_cream)  #not persisted
ice_cream_saved  = create(:ice_cream) #persisted

What's more complicated is setting up associated data. As you saw above, setting up a belongs_to relationship is pretty simple. You just need to make sure you've defined a factory for the associated model, and then specify the model's name as an attribute in the factory you're working with.

Above, I was working with the Ice Cream factory, and each ice cream instance belongs to a parlor. So to set up the association, I simply wrote parlor.

Many-to-many relationships are more complex, but not impossible. Among the many cool things you can do with Factory Girl is nest factories such that the inner factories will inherit the outer factory's attributes. Below, I've nested the ice_cream_with_three_flavors factory within the generic ice_cream factory so that the ice_cream_with_three_flavors factory will in fact still be valid.

Also important to note is that I've defined a transient property that will be used in the after(:create) block. Using this syntax, you can start to see that you can compose additional factories pretty easily.

FactoryGirl.define do
  factory :ice_cream, class: IceCream do
    title { Faker::Food.ingredient }
    image { Faker::LoremPixel.image  }

    factory :ice_cream_with_three_flavors, class: IceCream do
      transient do
        flavors_count 3

      after(:create) do |ice_cream, evaluator|
        create_list(:flavor, evaluator.flavors_count, ice_creams: [ice_cream])
      # Ice creams have many flavors and flavors have many ice creams
      # So to get this association to work, I had to pass in the associated
      # model as an array to the `after(:create)` block

    factory :ice_cream_with_two_reviews, class: IceCream do
      transient do
        reviews_count 2

      after(:create) do |ice_cream, evaluator|
        create_list(:review, evaluator.reviews_count, ice_cream: ice_cream)
      # Here, ice creams have many reviews, so it's a one-to-many
      # relationship
      # This means that we can pass a singular ice_cream to each review and
      # set up the association correctly


Writing tests

Now let's say I'm writing tests for the associations. Here's how I would use those factories in a test.

require "rails_helper"

describe IceCream, type: :model do
  describe "associations" do
    it "has many flavors" do
      ice_cream_with_flavors = create(:ice_cream_with_three_flavors)
      expect(ice_cream_with_flavors.flavors.count).to eq(3)

    it "has many reviews" do
      ice_cream_with_reviews = create(:ice_cream_with_two_reviews)
      expect( eq(2)


And that's it! Hopefully this will inspire you to write tests as well! As I've been writing code, I've started to see the light: Tests save you from yourself.