# factory_boy

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

As a fixtures replacement tool, it aims to replace static, hard to maintain fixtures with easy-to-use factories for complex objects.

Instead of building an exhaustive test setup with every possible combination of corner cases, `factory_boy` allows you to use objects customized for the current test, while only declaring the test-specific fields:

    class FooTests(unittest.TestCase):

        def test_with_factory_boy(self):
            # We need a 200€, paid order, shipping to australia, for a VIP customer
            order = OrderFactory(
                amount=200,
                status='PAID',
                customer__is_vip=True,
                address__country='AU',
            )
            # Run the tests here

        def test_without_factory_boy(self):
            address = Address(
                street="42 fubar street",
                zipcode="42Z42",
                city="Sydney",
                country="AU",
            )
            customer = Customer(
                first_name="John",
                last_name="Doe",
                phone="+1234",
                email="john.doe@example.org",
                active=True,
                is_vip=True,
                address=address,
            )
            # etc.

factory_boy is designed to work well with various ORMs (Django, MongoDB, SQLAlchemy), and can easily be extended for other libraries.

Its main features include:

- Straightforward declarative syntax

- Chaining factory calls while retaining the global context

- Support for multiple build strategies (saved/unsaved instances, stubbed objects)

- Multiple factories per class support, including inheritance

## Links

- Documentation: https://factoryboy.readthedocs.io/

- Repository: https://github.com/FactoryBoy/factory_boy

- Package: https://pypi.org/project/factory-boy/

- Mailing-list: factoryboy@googlegroups.com | https://groups.google.com/forum/#!forum/factoryboy

## Download

PyPI: https://pypi.org/project/factory-boy/

    $ pip install factory_boy

Source: https://github.com/FactoryBoy/factory_boy/

    $ git clone git://github.com/FactoryBoy/factory_boy/
    $ python setup.py install

## Usage

Note

This section provides a quick summary of factory_boy features. A more detailed listing is available in the full documentation.

### Defining factories

Factories declare a set of attributes used to instantiate a Python object. The class of the object must be defined in the `model` field of a `class Meta:` attribute:

    import factory
    from . import models

    class UserFactory(factory.Factory):
        class Meta:
            model = models.User

        first_name = 'John'
        last_name = 'Doe'
        admin = False

    # Another, different, factory for the same object
    class AdminFactory(factory.Factory):
        class Meta:
            model = models.User

        first_name = 'Admin'
        last_name = 'User'
        admin = True

### ORM integration

factory_boy integration with Object Relational Mapping (ORM) tools is provided through specific `factory.Factory` subclasses:

- Django, with `factory.django.DjangoModelFactory`

- Mogo, with `factory.mogo.MogoFactory`

- MongoEngine, with `factory.mongoengine.MongoEngineFactory`

- SQLAlchemy, with `factory.alchemy.SQLAlchemyModelFactory`

More details can be found in the ORM section.

### Using factories

factory_boy supports several different instantiation strategies: build, create, and stub:

    # Returns a User instance that's not saved
    user = UserFactory.build()

    # Returns a saved User instance.
    # UserFactory must subclass an ORM base class, such as DjangoModelFactory.
    user = UserFactory.create()

    # Returns a stub object (just a bunch of attributes)
    obj = UserFactory.stub()

You can use the Factory class as a shortcut for the default instantiation strategy:

    # Same as UserFactory.create()
    user = UserFactory()

No matter which strategy is used, it’s possible to override the defined attributes by passing keyword arguments:

    # Build a User instance and override first_name
    >>> user = UserFactory.build(first_name='Joe')
    >>> user.first_name
    "Joe"

It is also possible to create a bunch of objects in a single call:

    >>> users = UserFactory.build_batch(10, first_name="Joe")
    >>> len(users)
    10
    >>> [user.first_name for user in users]
    ["Joe", "Joe", "Joe", "Joe", "Joe", "Joe", "Joe", "Joe", "Joe", "Joe"]

### Realistic, random values

Demos look better with random yet realistic values; and those realistic values can also help discover bugs. For this, factory_boy relies on the excellent faker library:

    class RandomUserFactory(factory.Factory):
        class Meta:
            model = models.User

        first_name = factory.Faker('first_name')
        last_name = factory.Faker('last_name')

    >>> RandomUserFactory()
    <User: Lucy Murray>

### Reproducible random values

The use of fully randomized data in tests is quickly a problem for reproducing broken builds. To that purpose, factory_boy provides helpers to handle the random seeds it uses, located in the `factory.random` module:

    import factory.random

    def setup_test_environment():
        factory.random.reseed_random('my_awesome_project')
        # Other setup here

### Lazy Attributes

Most factory attributes can be added using static values that are evaluated when the factory is defined, but some attributes (such as fields whose value is computed from other elements) will need values assigned each time an instance is generated.

These “lazy” attributes can be added as follows:

    class UserFactory(factory.Factory):
        class Meta:
            model = models.User

        first_name = 'Joe'
        last_name = 'Blow'
        email = factory.LazyAttribute(lambda a: '{}.{}@example.com'.format(a.first_name, a.last_name).lower())
        date_joined = factory.LazyFunction(datetime.now)

    >>> UserFactory().email
    "joe.blow@example.com"

Note

`LazyAttribute` calls the function with the object being constructed as an argument, when `LazyFunction` does not send any argument.

### Sequences

Unique values in a specific format (for example, e-mail addresses) can be generated using sequences. Sequences are defined by using `Sequence` or the decorator `sequence`:

    class UserFactory(factory.Factory):
        class Meta:
            model = models.User

        email = factory.Sequence(lambda n: 'person{}@example.com'.format(n))

    >>> UserFactory().email
    'person0@example.com'
    >>> UserFactory().email
    'person1@example.com'

### Associations

Some objects have a complex field, that should itself be defined from a dedicated factories. This is handled by the `SubFactory` helper:

    class PostFactory(factory.Factory):
        class Meta:
            model = models.Post

        author = factory.SubFactory(UserFactory)

The associated object’s strategy will be used:

    # Builds and saves a User and a Post
    >>> post = PostFactory()
    >>> post.id is None  # Post has been 'saved'
    False
    >>> post.author.id is None  # post.author has been saved
    False

    # Builds but does not save a User, and then builds but does not save a Post
    >>> post = PostFactory.build()
    >>> post.id is None
    True
    >>> post.author.id is None
    True

## Support Policy

`factory_boy` supports active Python versions as well as PyPy3.

- Python’s supported versions.

- Django’s supported versions.

- SQLAlchemy: latest version on PyPI.

- MongoEngine: latest version on PyPI.

## Debugging factory_boy

Debugging factory_boy can be rather complex due to the long chains of calls. Detailed logging is available through the `factory` logger.

A helper, factory.debug(), is available to ease debugging:

    with factory.debug():
        obj = TestModel2Factory()

    import logging
    logger = logging.getLogger('factory')
    logger.addHandler(logging.StreamHandler())
    logger.setLevel(logging.DEBUG)

This will yield messages similar to those (artificial indentation):

    BaseFactory: Preparing tests.test_using.TestModel2Factory(extra={})
      LazyStub: Computing values for tests.test_using.TestModel2Factory(two=<OrderedDeclarationWrapper for <factory.declarations.SubFactory object at 0x1e15610>>)
        SubFactory: Instantiating tests.test_using.TestModelFactory(__containers=(<LazyStub for tests.test_using.TestModel2Factory>,), one=4), create=True
        BaseFactory: Preparing tests.test_using.TestModelFactory(extra={'__containers': (<LazyStub for tests.test_using.TestModel2Factory>,), 'one': 4})
          LazyStub: Computing values for tests.test_using.TestModelFactory(one=4)
          LazyStub: Computed values, got tests.test_using.TestModelFactory(one=4)
        BaseFactory: Generating tests.test_using.TestModelFactory(one=4)
      LazyStub: Computed values, got tests.test_using.TestModel2Factory(two=<tests.test_using.TestModel object at 0x1e15410>)
    BaseFactory: Generating tests.test_using.TestModel2Factory(two=<tests.test_using.TestModel object at 0x1e15410>)

## Contributing

factory_boy is distributed under the MIT License.

Issues should be opened through GitHub Issues; whenever possible, a pull request should be included. Questions and suggestions are welcome on the mailing-list.

Development dependencies can be installed in a virtualenv with:

    $ pip install --editable '.[dev]'

All pull requests should pass the test suite, which can be launched simply with:

    $ make testall

In order to test coverage, please use:

    $ make coverage

To test with a specific framework version, you may use a `tox` target:

    # list all tox environments
    $ tox --listenvs

    # run tests inside a specific environment (django/mongoengine/SQLAlchemy are not installed)
    $ tox -e py310

    # run tests inside a specific environment (django)
    $ tox -e py310-djangomain

    # run tests inside a specific environment (alchemy)
    $ tox -e py310-alchemy

    # run tests inside a specific environment (mongoengine)
    $ tox -e py310-mongo

## Packaging

For users interesting in packaging FactoryBoy into downstream distribution channels (e.g. `.deb`, `.rpm`, `.ebuild`), the following tips might be helpful:

### Dependencies

The package’s run-time dependencies are listed in `setup.cfg`. The dependencies useful for building and testing the library are covered by the `dev` and `doc` extras.

Moreover, all development / testing tasks are driven through `make(1)`.

### Building

In order to run the build steps (currently only for docs), run:

    python setup.py egg_info
    make doc

### Testing

When testing for the active Python environment, run the following:

    make test

Note

You must make sure that the `factory` module is importable, as it is imported from the testing code.

## Contents, indices and tables

- Introduction
  - Basic usage
  - Sequences
  - LazyFunction
  - LazyAttribute
  - Inheritance
  - Non-kwarg arguments
  - Altering a factory’s behavior: parameters and traits
  - Strategies
- Reference
  - The `Factory` class
  - Declarations
  - Module-level functions
  - Randomness management
- Using factory_boy with ORMs
  - Django
  - Mogo
  - MongoEngine
  - SQLAlchemy
- Common recipes
  - Dependent objects (ForeignKey)
  - Reverse dependencies (reverse ForeignKey)
  - Simple Many-to-many relationship
  - Many-to-many relation with a ‘through’
  - Copying fields to a SubFactory
  - Custom manager methods
  - Forcing the sequence counter
  - Using reproducible randomness
  - Converting a factory’s output to a dict
  - Fuzzying Django model field choices
  - Django models with GenericForeignKeys
- Fuzzy attributes
  - FuzzyAttribute
  - FuzzyText
  - FuzzyChoice
  - FuzzyInteger
  - FuzzyDecimal
  - FuzzyFloat
  - FuzzyDate
  - FuzzyDateTime
  - FuzzyNaiveDateTime
  - Custom fuzzy fields
- Examples
  - Objects
  - Factories
  - Using the factories
- Internals
  - Parsing, Step 1: Metaclass and type declaration
  - Parsing, Step 2: adapting the class definition
  - Instantiating, Step 1: Converging entry points
  - Instantiating, Step 2: Preparing values
  - Instantiating, Step 3: Building the object
- ChangeLog
  - 3.3.3 (2025-02-03)
  - 3.3.2 (2025-02-03)
  - 3.3.1 (2024-08-18)
  - 3.3.0 (2023-07-19)
  - 3.2.1 (2021-10-26)
  - 3.2.0 (2020-12-28)
  - 3.1.0 (2020-10-02)
  - 3.0.1 (2020-08-13)
  - 3.0.0 (2020-08-12)
  - 2.12.0 (2019-05-11)
  - 2.11.1 (2018-05-05)
  - 2.11.0 (2018-05-05)
  - 2.10.0 (2018-01-28)
  - 2.9.2 (2017-08-03)
  - 2.9.1 (2017-08-02)
  - 2.9.0 (2017-07-30)
  - 2.8.1 (2016-12-17)
  - 2.8.0 (2016-12-17)
  - 2.7.0 (2016-04-19)
  - 2.6.1 (2016-02-10)
  - 2.6.0 (2015-10-20)
  - 2.5.2 (2015-04-21)
  - 2.5.1 (2015-03-27)
  - 2.5.0 (2015-03-26)
  - 2.4.1 (2014-06-23)
  - 2.4.0 (2014-06-21)
  - 2.3.1 (2014-01-22)
  - 2.3.0 (2013-12-25)
  - 2.2.1 (2013-09-24)
  - 2.2.0 (2013-09-24)
  - 2.1.2 (2013-08-14)
  - 2.1.1 (2013-07-02)
  - 2.1.0 (2013-06-26)
  - 2.0.2 (2013-04-16)
  - 2.0.1 (2013-04-16)
  - 2.0.0 (2013-04-15)
  - 1.3.0 (2013-03-11)
  - 1.2.0 (2012-09-08)
  - 1.1.5 (2012-07-09)
  - 1.1.4 (2012-06-19)
  - 1.1.3 (2012-03-09)
  - 1.1.2 (2012-02-25)
  - 1.1.1 (2012-02-24)
  - 1.1.0 (2012-02-24)
  - 1.0.4 (2011-12-21)
  - 1.0.2 (2011-05-16)
  - 1.0.1 (2011-05-13)
  - 1.0.0 (2010-08-22)
  - Credits
- Credits
  - Maintainers
  - Contributors
  - Contributor license agreement
- Ideas

- Index

- Module Index

- Search Page