具有 OneToOne 关系和相关字段的 django factory boy factory

Question

I am using Factory Boy to create test factories for my django app. The model I am having an issue with is a very basic Account model which has a OneToOne relation to the django User auth model (using django < 1.5):

# models.py
from django.contrib.auth.models import User
from django.db import models

class Account(models.Model):
    user = models.OneToOneField(User)
    currency = models.CharField(max_length=3, default='USD')
    balance = models.CharField(max_length="5", default='0.00') 

Here are my factories:

# factories.py
from django.db.models.signals import post_save
from django.contrib.auth.models import User

import factory

from models import Account


class AccountFactory(factory.django.DjangoModelFactory):
    FACTORY_FOR = Account

    user = factory.SubFactory('app.factories.UserFactory')
    currency             = 'USD'
    balance              = '50.00'

class UserFactory(factory.django.DjangoModelFactory):
    FACTORY_FOR = User

    username = 'bob'
    account = factory.RelatedFactory(AccountFactory)

So I am expecting the factory boy to create a related UserFactory whenever AccountFactory is invoked:

# tests.py 
from django.test import TestCase

from factories import AccountFactory

class AccountTest(TestCase):

    def setUp(self):
        self.factory = AccountFactory()

    def test_factory_boy(self):
        print self.factory.id

When running the test however, it looks like multiple User models are being create, and I am seeing an integriy error:

IntegrityError: column username is not unique

The documentation does mention watching out for loops when dealing with circular imports, but I am not sure whether that is whats going on, nor how I would remedy it. docs

If anyone familiar with Factory Boy could chime in or provide some insight as to what may be causing this integrity error it would be much appreciated!

Answer 1

I believe this is because you have a circular reference in your factory definitions. Try removing the line account = factory.RelatedFactory(AccountFactory) from the UserFactory definition. If you are always going to invoke the account creation through AccountFactory, then you shouldn't need this line.

Also, you may consider attaching a sequence to the name field, so that if you ever do need more than one account, it'll generate them automatically.

Change: username = "bob" to username = factory.Sequence(lambda n : "bob {}".format(n)) and your users will be named "bob 1", "bob 2", etc.

Answer 2

To pass result of calling UserFactory to AccountFactory you should use factory_related_name ( docs )

Code above works next way:

• AccountFactory for instantiating needs SubFactory(UserFactory) .
• UserFactory instantiates User.
• UserFactory after instantiating calls RelatedFactory(AccountFactory)
• Recursion,.. that is broken due to unique username constraint (you probably want to generate usernames via FuzzyText or Sequence )

So you need write UserFactory like this:

class UserFactory(factory.django.DjangoModelFactory):
    account = factory.RelatedFactory(AccountFactory, factory_related_name='user')
    username = factory.Sequence(lambda a: 'email%04d@somedomain.com' % a)
    # rest of code

But you can still experience issues with already written tests. Imagine you have in tests places like next:

user = UserFactory()
account = Account(user=user)

Then adding RelatedFactory will break tests. If you haven't lots of tests and contributors in your project, you could rewrite them. But if not, it is not an option. Here is how it could be handled:

class UserFactory(factory.django.DjangoModelFactory):
    class Params:
        generate_account = factory.Trait(
            account=factory.RelatedFactory(AccountFactory, factory_related_name='user')
        )

Then code above won't be broken, because default call of UserFactory won't instantiate AccountFactory . To instantiate user with account:

user_with_account = UserFactory(generate_account=True)