问题
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!
回答1:
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
回答2:
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).
回答3:
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.
来源：https://stackoverflow.com/questions/14098031/whats-the-difference-between-the-build-and-create-methods-in-factorygirl