CODEWITHSUNDEEP
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Son of the Wai-Pan
Son of the Wai-Pan

Reputation: 13221

What's the difference between the build and create methods in FactoryGirl?

The Factory Girl introduction delineates the difference between FactoryGirl.build() and FactoryGirl.create():

# Returns a User instance that's not saved
user = FactoryGirl.build(:user)

# Returns a saved User instance
user = FactoryGirl.create(:user)

I still don't understand the practical differences between the two. Can someone give an example where you would want to use one and not the other? Thanks!

Upvotes: 117

Views: 67528

Answers (3)

Nesha Zoric
Nesha Zoric

Reputation: 6650

FactoryGirl.create() will create new object and associations (if the factory has any) for it. They will all be persisted in a database. Also, it will trigger both model and database validations. Callbacks after(:build) and after(:create) will be called after the factory is saved. Also before(:create) will be called before the factory is saved.

FactoryGirl.build() won't save an object, but will still make requests to a database if the factory has associations. It will trigger validations only for associated objects. Callback after(:build) will be called after the factory is built.

Note that in most cases when testing models are best to use build_stubbed for better performance. Read more about it here.

Upvotes: 6

Helio Santos
Helio Santos

Reputation: 6815

The create() method persists the instance of the model while the build() method keeps it only on memory.

Personally, I use the create() method only when persistence is really necessary since writing to DB makes testing time consuming.

e.g.

I create users to authentication with create() because my authentication engine queries the DB.

To check if a model has an attribute the build() method will do because no DB access is required.

it{Factory.build(:user).should respond_to(:name)}

Update

"There is one exception that build actually 'creates' when you are building associations, i.e your association are no longer in memory but persisted. Keep that in mind" – Shakes

Upvotes: 150

chasm
chasm

Reputation: 381

Using FactoryGirl.build(:factory_name) does not persist to the db and does not call save!, so your Active Record validations will not run. This is much faster, but validations might be important.

Using FactoryGirl.create(:factory_name) will persist to the db and will call Active Record validations. This is obviously slower but can catch validation errors (if you care about them in your tests).

Upvotes: 22

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