factory_boy

what is it?

factory_boy is a fixtures replacement tool based on thoughtbot’s factory_bot

it aims to replace static, hard to maintain fixtures with easy-to-use factories for complex objects

using factory_boy with ORMs

django

all factories for a django model should use the DjangoModelFactory base class

DjangoModelFactory provides the following features

• model attribute also supports the 'app.Model' syntax
• create() uses Model.objects.create()
• when using RelatedFactory or PostGeneration attributes, the base object will be saved once all post-generation hooks have run.

class UserFactory(DjangoModelFactory):
    class Meta:
        model = User
 
    username = Faker("user_name")
    email = LazyAttribute(lambda o: '%s@example.com' % o.username)
    password = LazyAttribute(lambda o: make_password(o.username))
    first_name = Faker("first_name")
    last_name = Faker("last_name")

• to not save the instance to db and build in memory, use build()

  user = UserFactory.build()

LazyAttribute

building block for extending a factory

takes as argument a method to call (usually a lambda); that method should accept the object being built as sole argument, and return a value

class UserFactory(factory.Factory):
    class Meta:
        model = User
 
    username = 'john'
    email = factory.LazyAttribute(lambda o: '%s@example.com' % o.username)

Faker

wrapper around faker; its argument is the name of a faker provider

can use previous attribute in Faker:

class TripFactory(factory.Factory):
    class Meta:
        model = Trip
 
    departure = factory.Faker(
        'date',
        end_datetime=datetime.date.today(),
    )
    arrival = factory.Faker(
        'date_between_dates',
        date_start=factory.SelfAttribute('..departure'),
    )