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Rails faker gem overview | BootrAils

The faker gem for Rails is right here to assist your take a look at database to be seeded with real-looking take a look at knowledge. Let’s have a look at how.

What’s Faker?

Throughout the improvement course of, it’s usually obligatory to check the applying to work with actual knowledge. Furthermore, the info ought to be as shut as doable to the true ones, each qualitatively and quantitatively, particularly if we wish to add tons of of information to our database. Fortunately, there’s a gem referred to as Faker, that vastly simplifies the work of filling the database with such knowledge (telephone numbers, electronic mail, usernames, and so forth.) that you need to use in your checks. Because it talked about within the repository description, Faker generates knowledge at random, so returned values aren’t assured to be distinctive by default. However you possibly can explicitly specify once you require distinctive values following the directions.

Create an empty Rails app

Let’s create our model new Rails software.

There’s numerous methods to create Rails apps, however the best and cleanest manner in all probability is to create a file named Gemfile in your working listing, and fill it like this:

supply ''

ruby '3.0.2'

gem 'rails', '~>'

After which run

bundle set up

Verify this inside the listing the place you need your Rails 7 app to stay:

rails -v



If that works, then you definitely’re accomplished with the conditions.

So we will now create our software.

rails new APP_NAME --database=postgresql
  • rails is the Rails CLI (command line interface) software
  • new tells the Rails CLI that we wish to generate a brand new software
  • APP_NAME is, effectively, your app title
  • –database=postgresql is an non-obligatory parameter that tells Rails we wish to use the PostgreSQL to persist our knowledge (by default Rails has SQLite database)

After producing your new Rails app, you’ll must cd into your new app and create your database.

Run at terminal

rails db:create


rails db:migrate

Good! Now run up your improvement server

rails s

Be sure you can navigate to your browser at localhost:3000, and if every part has gone effectively, it is best to see the Rails default index web page.

Now let’s add a few fashions so now we have one thing to work with:

rails g mannequin Person title:string
rails g mannequin Put up title:string physique:textual content person:belongs_to

after which

rails db:migrate

Nothing uncommon occurs right here: a message with a header, a physique, an affiliation for the person.

Make certain the proper associations are created, in addition to some easy validations:

# inside fashions/person.rb
has_many :posts
validates :title, presence: true
# inside fashions/submit.rb
belongs_to :person
validates :title, presence: true
validates :physique, presence: true

The subsequent step is to load a number of cases of the information into the newly created tables.

Add the faker gem

The best approach to load some knowledge is to make use of the seeds.rb file contained in the db listing. Nonetheless, like many programmers, I do not wish to take into consideration any content material throughout improvement. So why do not we reap the benefits of the Faker gem, which might generate random knowledge of assorted sorts: names, emails, texts, even film quotes and extra.

First add Faker gem to Gemfile

supply ""

gem "rails", "~> 7.0.3", ">="

gem 'faker'


bundle set up

Or simply by inserting the next into the command line of your terminal

gem set up faker

Faker will then be globally obtainable to make use of inside your mission.

Add a seed file

Subsequent, we’ll add a Rake process to populate the database with pattern knowledge, for which Rails has a default location of db/seeds.rb.

Person.create!(title:  "Lone Person",
             electronic mail: "take a look")

99.occasions do |n|
  title  = Faker::Title.title
  electronic mail = Faker::Web.electronic mail
  Person.create!(title:  title,
               electronic mail: electronic mail)
# and one other form of syntax for including posts for our customers
  Person.posts.create({title: Faker::Hipster.sentence, physique: Faker::Lorem.sentence})

Within the case of the primary person (Lone Person), there’s an instance of how we will create customers from seeds.rb with out Faker, after we do not want extra knowledge.
One other 99 customers have been populated with the gem. And in addition 99 posts with the title and textual content by the authorship of those customers. For every loop you might be creating a brand new person and a brand new submit.

As you possibly can see we use create! right here, the bang model of create. So what’s this for? Our create! will elevate an exception if it encounters an error whereas seeding and the database will cease seeding however information seeded earlier than the exception will stay within the database. What if we have been to make use of create? The seeds.rb code will run to completion however creation of some information could silently fail.

There may very well be a lot of causes when utilizing create! throw an exception. The most typical cause is often that the report did not validate. As a result of validations apply to all information, no matter whether or not they’re created within the software, within the Rails console, or in a seed file.

So create! will throw the precise validation error if a report fails to seed as a result of it is not validated. To repair this situation, it is best to replace your seeds.rb code so that every one information may be correctly validated and created within the database. And utilizing create as an alternative of create! just isn’t the appropriate manner. The primary objective if we ask our seeds.rb file to create any quantity of information within the database, to know that we’ll get precisely that very same variety of information.

Load demo knowledge

Lastly, load the info:

rails db:seed

Notice, that Faker::Title.title, Faker::Hipster.sentence and Faker::Lorem.sentence are normal Turbines from Faker README the place you’ll find all the present turbines and outline of their utilization. The way you make the most of the gem is dependent upon the kind of knowledge you may be searching for.

In case you have a mannequin attribute which has a uniqueness validation Faker has a novel methodology you can also make use of:


This can return a novel title each time it’s referred to as. That is helpful if you’re creating quite a few objects with distinctive attributes with checks i.e. in case you’re utilizing a create_list with FactoryBot:

create_list(:article, 5, title: Faker::Lorem.distinctive.sentence)
# it will create 5 articles with distinctive titles

Typically Faker creates knowledge that’s larger than you want. On this case you possibly can minimize it by modifying Turbines like this:

Person.submit.title = Faker::E-book.title[0..30]
# it can get solely the primary 30 characters


Person.submit.title = Faker::Hipster.sentence(word_count: 3)
# it can get solely the primary 3 phrases

All of those and extra you can see on the Faker README.


We now have come to the tip of the article. Hopefully, by now, you’ll really feel extra assured in utilizing the Faker gem.

The Faker gem is very easy to combine into your Rails software and generates enormous quantities of knowledge for testing throughout improvement. Additionally, Faker is nice to make use of inside RSpec to faux out knowledge and hold your checks trying extra streamlined.



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