How to create has_and_belongs_to_many associations in Factory girl

Question

Given the following

class User < ActiveRecord::Base
  has_and_belongs_to_many :companies
end

class Company < ActiveRecord::Base
  has_and_belongs_to_m         


        

Answer 1

You can define new factory and use after(:create) callback to create a list of associations. Let's see how to do it in this example:

FactoryBot.define do

  # user factory without associated companies
  factory :user do
    # user attributes

    factory :user_with_companies do
      transient do
        companies_count 10
      end

      after(:create) do |user, evaluator|
        create_list(:companies, evaluator.companies_count, user: user)
      end
    end
  end
end

Attribute companies_count is a transient and available in attributes of the factory and in the callback via the evaluator. Now, you can create a user with companies with the option to specify how many companies you want:

create(:user_with_companies).companies.length # 10
create(:user_with_companies, companies_count: 15).companies.length # 15