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

What worked for me was setting the association when using the factory. Using your example:

user = Factory(:user)
company = Factory(:company)

company.users << user 
company.save! 

Answer 2

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

Answer 3

Found this way nice and verbose:

FactoryGirl.define do
  factory :foo do
    name "Foo" 
  end

  factory :bar do
    name "Bar"
    foos { |a| [a.association(:foo)] }
  end
end

Answer 4

Update for Rails 5:

Instead of using has_and_belongs_to_many association, you should consider: has_many :through association.

The user factory for this association looks like this:

FactoryBot.define do
  factory :user do
    # user attributes

    factory :user_with_companies do
      transient do
        companies_count 10 # default number
      end

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

You can create the company factory in a similar way.

Once both factories are set, you can create user_with_companies factory with companies_count option. Here you can specify how many companies the user belongs to: create(:user_with_companies, companies_count: 15)

You can find detailed explanation about factory girl associations here.

Answer 5

First of all I strongly encourage you to use has_many :through instead of habtm (more about this here), so you'll end up with something like:

Employment belongs_to :users
Employment belongs_to :companies

User has_many :employments
User has_many :companies, :through => :employments 

Company has_many :employments
Company has_many :users, :through => :employments

After this you'll have has_many association on both sides and can assign to them in factory_girl in the way you did it.