A faker gem is used to create the fake data for testing or demo purpose in rails application. It is Perl's Data::Faker library that generate different type (i.e. Address, color, code, commerce, company, date etc.) of fake data. We are generally using this gem to feed the fake records during application development. The implementation of faker gem give as below...

Step1: Add faker gem into Gemfile

Path: my_app/Gemfile

gem install faker

Step2: Run bundler

bundle install

 Now, we can use the fake data in our application.

Feed fake data into table: If we require some data during application development, we can feed by seed.rb file

For example : Suppose we have a table users with columns first_name, last_name, email, address, phone and need some data during development, so we can feed data into table by below code...

Add below code into seeds.rb

Path: my_app/db/seeds.rb

(0..50).each do |p|
  User.create(fist_name: Faker::Name.first_name, last_name: Faker::Name.last_name, email: Faker::Internet.email , address: Faker::Address.street_address , phone: Faker::Number.number(10) )
 # puts "Created #{p}"
end

Then run

rake db:seed

Finally our users table filled with 50 records.We can also use this gem into test case.

For example: we are going to write a model unit  test-case for has_many association between country & city using faker gem data

def test_country_has_many_cities_association
    country = create(:country, :name => Faker::Address.country,  :code => Faker::Address.country_code)
    c1 = create(:city, country_id: country.id, :city_name => Faker::Address.city, :zip => Faker::Address.zip_code )
    c2 = create(:city, country_id: country.id, :city_name => Faker::Address.city, :zip => Faker::Address.zip_code)

    assert_equal country.cities, [c1,c2]
  end