path: root/README

factory_boy
===========

.. image:: https://secure.travis-ci.org/rbarrois/factory_boy.png?branch=master
    :target: http://travis-ci.org/rbarrois/factory_boy/

factory_boy is a fixtures replacement based on thoughtbot's `factory_girl <http://github.com/thoughtbot/factory_girl>`_.

Its features include:

- Straightforward syntax
- Support for multiple build strategies (saved/unsaved instances, attribute dicts, stubbed objects)
- Powerful helpers for common cases (sequences, sub-factories, reverse dependencies, circular factories, ...)
- Multiple factories per class support, including inheritance
- Support for various ORMs (currently Django, Mogo)

The official repository is at http://github.com/rbarrois/factory_boy; the documentation at http://readthedocs.org/docs/factoryboy/.

factory_boy supports Python 2.6 and 2.7 (Python 3 is in the works), and requires only the standard Python library.


Download
--------

Github: http://github.com/rbarrois/factory_boy/

PyPI:

.. code-block:: sh

    $ pip install factory_boy

Source:

.. code-block:: sh

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


Defining factories
------------------

Factories declare a set of attributes used to instantiate an object. The class of the object must be defined in the FACTORY_FOR attribute:

.. code-block:: python

    import factory
    from models import User

    class UserFactory(factory.Factory):
        FACTORY_FOR = User

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

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

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


Using factories
---------------

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

.. code-block:: python

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

    # Returns a saved User instance
    user = UserFactory.create()

    # Returns a dict of attributes that can be used to build a User instance
    attributes = UserFactory.attributes()


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

.. code-block:: python

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


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

.. code-block:: pycon

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


Lazy Attributes
---------------

Most factory attributes can be added using static values that are evaluated when the factory is defined, but some attributes (such as associations and other attributes that must be dynamically generated) will need values assigned each time an instance is generated. These "lazy" attributes can be added as follows:

.. code-block:: python

    class UserFactory(factory.Factory):
        first_name = 'Joe'
        last_name = 'Blow'
        email = factory.LazyAttribute(lambda a: '{0}.{1}@example.com'.format(a.first_name, a.last_name).lower())

.. code-block:: pycon

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


The function passed to ``LazyAttribute`` is given the attributes defined for the factory up to the point of the LazyAttribute declaration. If a lambda won't cut it, the ``lazy_attribute`` decorator can be used to wrap a function:

.. code-block:: python

    # Stub factories don't have an associated class.
    class SumFactory(factory.StubFactory):
        lhs = 1
        rhs = 1

        @lazy_attribute
        def sum(a):
            result = a.lhs + a.rhs  # Or some other fancy calculation
            return result


Associations
------------

Associated instances can also be generated using ``SubFactory``:

.. code-block:: python

    from models import Post

    class PostFactory(factory.Factory):
        author = factory.SubFactory(UserFactory)


The associated object's strategy will be used:


.. code-block:: python

    # Builds and saves a User and a Post
    post = PostFactory()
    post.id == None           # => False
    post.author.id == None    # => False

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


Inheritance
-----------

You can easily create multiple factories for the same class without repeating common attributes by using inheritance:

.. code-block:: python

    class PostFactory(factory.Factory):
        title = 'A title'

    class ApprovedPost(PostFactory):
        approved = True
        approver = factory.SubFactory(UserFactory)


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``:

.. code-block:: python

    class UserFactory(factory.Factory):
        email = factory.Sequence(lambda n: 'person{0}@example.com'.format(n))

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

Sequences can be combined with lazy attributes:

.. code-block:: python

    class UserFactory(factory.Factory):
        name = 'Mark'
        email = factory.LazyAttributeSequence(lambda a, n: '{0}+{1}@example.com'.format(a.name, n).lower())

    UserFactory().email  # => mark+0@example.com

If you wish to use a custom method to set the initial ID for a sequence, you can override the ``_setup_next_sequence`` class method:

.. code-block:: python

    class MyFactory(factory.Factory):

        @classmethod
        def _setup_next_sequence(cls):
            return cls.FACTORY_FOR.objects.values_list('id').order_by('-id')[0] + 1

Customizing creation
--------------------

Sometimes, the default build/create by keyword arguments doesn't allow for enough
customization of the generated objects. In such cases, you should override the
Factory._prepare method:

.. code-block:: python

    class UserFactory(factory.Factory):
        @classmethod
        def _prepare(cls, create, **kwargs):
            password = kwargs.pop('password', None)
            user = super(UserFactory, cls)._prepare(create, **kwargs)
            if password:
                user.set_password(password)
                if create:
                    user.save()
            return user

.. OHAI VIM**

Subfactories
------------

If one of your factories has a field which is another factory, you can declare it as a ``SubFactory``. This allows to define attributes of that field when calling
the global factory, using a simple syntax : ``field__attr=42`` will set the attribute ``attr`` of the ``SubFactory`` defined in ``field`` to 42:

.. code-block:: python

    class InnerFactory(factory.Factory):
        foo = 'foo'
        bar = factory.LazyAttribute(lambda o: foo * 2)

    class ExternalFactory(factory.Factory):
        inner = factory.SubFactory(InnerFactory, foo='bar')

    >>> e = ExternalFactory()
    >>> e.foo
    'bar'
    >>> e.bar
    'barbar'

    >>> e2 : ExternalFactory(inner__bar='baz')
    >>> e2.foo
    'bar'
    >>> e2.bar
    'baz'

Abstract factories
------------------

If a ``Factory`` simply defines generic attribute declarations without being bound to a given class,
it should be marked 'abstract' by declaring ``FACTORY_ABSTRACT = True``.
Such factories cannot be built/created/....

.. code-block:: python

    class AbstractFactory(factory.Factory):
        FACTORY_ABSTRACT = True
        foo = 'foo'

    >>> AbstractFactory()
    Traceback (most recent call last):
      ...
    AttributeError: type object 'AbstractFactory' has no attribute '_associated_class'


Contributing
============

factory_boy is distributed under the MIT License.

Issues should be opened through `GitHub Issues <http://github.com/rbarrois/factory_boy/issues/>`_; whenever possible, a pull request should be included.

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

.. code-block:: sh

    $ python setup.py test


In order to test coverage, please use:

.. code-block:: sh

    $ pip install coverage
    $ coverage erase; coverage run --branch setup.py test; coverage report


Contents, indices and tables
============================

.. toctree::
    :maxdepth: 2

    examples
    subfactory
    post_generation
    changelog

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`