factory_boy: a test fixtures replacement based on thoughtbot's factory_girl for Ruby

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+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.
+
+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 written by Mark Sandstrom.
+
+Thank you Joe Ferris and thoughtbot for creating factory_girl.
+
+Download
+--------
+
+Github: http://github.com/dnerdy/factory_boy/tree/master
+
+easy_install::
+    
+    easy_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 name of the factory is used to guess the class of the object by default, but it's possible to explicitly specify it::
+
+    import factory
+    from models import User
+    
+    # This will guess the User class
+    class UserFactory(factory.Factory):
+        first_name = 'John'
+        last_name = 'Doe'
+        admin = False
+        
+    # This will use the User class (Admin would have been guessed)
+    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::
+
+    # 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::
+
+    # Same as UserFactory.create()
+    user = UserFactory()
+    
+The default strategy can be overridden::
+
+    UserFactory.default_strategy = factory.BUILD_STRATEGY
+    user = UserFactory()
+    
+The default strategy can also be overridden for all factories::
+
+    # 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::
+
+    # 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::
+
+    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::
+
+    # 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``::
+
+    from models import Post
+    
+    class PostFactory(factory.Factory):
+        author = factory.LazyAttribute(lambda a: UserFactory())
+        
+The associated object's default strategy is always used::
+
+    # 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::
+
+    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``::
+
+    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::
+
+    class UserFactory(factory.Factory):
+        name = 'Mark'
+        email = factory.LazyAttributeSequence(lambda a, n: '{0}+{1}@example.com'.format(a.name, n).lower())
+        
+    UserFactory().email  # => mark+1@example.com