Factory Boy - An alternative for Fixtures

Factory Boy is a fixtures replacement tool. It allows you to use objects customized for the current test, while only declaring the test-specific fields.

Setting up your factories:

For testing the Django app, create a root directory named tests. Then create __init__.py, tests.py (to write your tests), factories.py (to write your model factories) in that directory.

So, your app layout looks like:

  myapp
    |- __init__.py
    |- admin.py
    |- forms.py
    |- models.py
    |- tests
        |- __init__.py
        |- factories.py
        |- tests.py
    |- urls.py
    |- views.py

Features of Factory Boy:

It allows you to automate much of the testing scenarios. Some examples are:

  1. Use a 'Sequence' object using a lambda function to dynamically create unique field values:
        EX: username = factory.Sequence(lambda n: 'user_%d' % n)

  2. Use a LazyAttribute object to pick from a range of choices for a defined field
        EX: choice = factory.LazyAttribute(lambda s: random.choice(dict(MyModel.CHOICES).keys()))

A basic factory: Factories declare a set of attributes used to instantiate an object. Here's a basic factory that generates auth.User instances:

# factories.py
from factory import DjangoModelFactory, lazy_attribute
from django.contrib.auth.models import User

class UserFactory(DjangoModelFactory):
    first_name = 'Shirisha'
    last_name = 'Gaddi'
    username = factory.Sequence(lambda n: 'user_%d' % n)
    email = lazy_attribute(lambda obj: obj.username + "@example.com")

    class Meta:
        model = 'User'
        django_get_or_create = ('username',)

Calling this as factories.UserFactory() will perform same task as User.objects.create call. Howerver, it is possible to override the defined attributes by passing keyword arguments:

# Create a user instance by overriding first_name
user = factories.UserFactory(first_name="Karuna")

The factory's Meta has django_get_or_create set, which means the factory will call the Django built-in User.objects.get_or_create method.

Posted On 11 June 2015 By MicroPyramid


About Micropyramid

Micropyramid is a software development and cloud consulting partner for enterprise businesses across the world. We work on python, Django, Salesforce, Angular, Reactjs, React Native, MySQL, PostgreSQL, Docker, Linux, Ansible, git, amazon web services. We are Amazon and salesforce consulting partner with 5 years of cloud architect experience. We develop e-commerce, retail, banking, machine learning, CMS, CRM web and mobile applications.


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