Why is factory_boy superior to using the ORM directly in tests?

Yes, you can prepare your test data by using django ORM directly. But there are advantages of using factories and factory_boy specifically, here are some of that I remember and use:

• your model factories are defined in a nice, clean and readable manner:

  class CasesFactory(factory.Factory):    FACTORY_FOR = models.Case    number = factory.Sequence(lambda n: '1021-{0}'.format(n))    create_date = datetime.datetime.now()

• another benefit of this class-based approach is the ability to create SubFactories

• also you can easily define factories for different kind of relationships: ForeignKey, reverse ForeignKey, ManyToMany (documentation)

• neat DjangoModelFactory class
• Sequences (as you've mentioned) helps make the data more "dynamic". Imagine handling it yourself.
• mute_signals decorator - sometimes while testing you don't want the signal to be dispatched

Basically, factory_boy is there to avoid writing "helper" functions for generating test data. Instead, it introduces a nice and easy-to-use interface to it.

Ask yourself: why reinvent the wheel is there is a tool specifically for the job?

Also see:

• Testing and Django (Carl Mayer's presentation)