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

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Avery picture Avery · Dec 31, 2012 · Viewed 43.9k times · Source

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 doesn'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!

Answer

Helio Santos picture Helio Santos · Jan 4, 2013

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

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