How to specify the association with factory_bot?

Question

For example I have two models a user and a post. A post belongs_to a user and a user has many posts

#spec/factories/post.rb
FactoryBot.define do
  factory :post do
    user
    body Faker::Movie.quote
    posted_at "2018-04-03 13:33:05"
  end
end

#spec/factories/user.rb
FactoryBot.define do 
  factory :user do 
    first_name 'Jake'
  end
end

Using Rspec in a test I want to do this:

user = create(:user, first_name: 'Barry') #id 1
post = create(:post, user: user)

I would expect that the user_id of post to be 1 however it is creating another user prior and the user_id is 2.

How can you specify the association when you are creating the object with factory_bot / factory_girl?

Solution 1

You should use explicit associations instead of implicit ones:

#spec/factories/post.rb
FactoryBot.define do
  factory :post do
    association :user    # <<<--- here the change
    body Faker::Movie.quote
    posted_at "2018-04-03 13:33:05"
  end
end

#spec/factories/user.rb
FactoryBot.define do 
  factory :user do 
    first_name 'Jake'
  end
end

https://github.com/thoughtbot/factory_bot/blob/master/GETTING_STARTED.md#associations

Solution 2

Another option is to use #trait method within the parent.

FactoryBot.define do
  factory :post do
    user nil
    body Faker::Movie.quote
    posted_at "2018-04-03 13:33:05"
  end
end

FactoryBot.define do 
  factory :user do 
    first_name 'Jake'
  end

  trait :with_post do
    after(:create) do |user|
      create(:post, user_id: user.id)
    end
  end
end

FactoryBot.create(:user, :with_post)

Solution 3

Here we have another solution in case your association name and factory name is different then you can follow below syntax.

#spec/factories/post.rb
FactoryBot.define do
  factory :post do
    association :author, factory: :user
    body Faker::Movie.quote
    posted_at "2018-04-03 13:33:05"
  end
end

in case your factory name is author and model name is user then you can use above syntax

Comments

[abax]

What does post.user.inspect and User.all return after you make the post?

[Jake McAllister]

post.user is User

[Jake McAllister]

and User.all is equal two users

[emptywalls]

Can you post your complete spec? Do you have any kind of authentication involved? If you have to login to run the spec, that could be the source of the other user.

[emptywalls]

Also, what the first_names in the records? Are they both Jake?

[Jake McAllister]

no its just that as a plain spec

[Jake McAllister]

to your second question first one has a first name of 'barry' and the second one has a first name of 'jake'

[Humayun Naseer]

factory :post do here post is pointing the actual model or this is created here ? & if this one is model & located within a module how can we locate it ?

[Ri1a]

Are there more arguments on why you should use explicit associations instead of implicit ones?

[Fran Martinez]

Using explicit associations is the only way to be able to override the attributes of the associated object. When the association is implicit, FactoryBot will create an associated object on which you don't have control of its attributes (it will automatically create an associated object based on the factory for that object). github.com/thoughtbot/factory_bot/blob/master/…