summaryrefslogtreecommitdiff
path: root/README
blob: b878d00058130ea11f447eea5d3564af1ad99f78 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
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>`_ . Like factory_girl it has a straightforward definition syntax, support for multiple build strategies (saved instances, unsaved instances, attribute dicts, and stubbed objects), and support for multiple factories for the same class, including factory inheritance. Django support is included, and support for other ORMs can be easily added.

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

Credits
-------

This README parallels the factory_girl README as much as possible; text and examples are reproduced for comparison purposes. Ruby users of factory_girl should feel right at home with factory_boy in Python.

factory_boy was originally written by Mark Sandstrom, and improved by Raphaƫl Barrois.

Thank you Joe Ferris and thoughtbot for creating factory_girl.

Download
--------

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

PyPI::

    pip install factory_boy

Source::

    # Download the source and run
    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()

    # Returns an object with all defined attributes stubbed out:
    stub = UserFactory.stub()

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

.. code-block:: python

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

The default strategy can be overridden:

.. code-block:: python

    UserFactory.default_strategy = factory.BUILD_STRATEGY
    user = UserFactory()

The default strategy can also be overridden for all factories:

.. code-block:: python

    # This will set the default strategy for all factories that don't define a default build strategy
    factory.Factory.default_strategy = factory.BUILD_STRATEGY

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

.. code-block:: python

    # 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())

    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 ``LazyAttribute``:

.. code-block:: python

    from models import Post

    class PostFactory(factory.Factory):
        author = factory.LazyAttribute(lambda a: UserFactory())

The associated object's default strategy is always used:

.. code-block:: python

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

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

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.LazyAttribute(lambda a: 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._associated_class.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

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 ``ABSTRACT_FACTORY = True``.
Such factories cannot be built/created/....

.. code-block:: python

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

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