added factory pattern

pypatterns/creational/factory.py

@@ -0,0 +1,21 @@
+from abc import abstractmethod, ABCMeta
+
+
+class Factory(object, metaclass=ABCMeta):
+    """
+    Abstract Factory Class.
+
+    All Factories should inherit this class and overwrite the create method.
+    """
+
+    @abstractmethod
+    def create(self, **kwargs):
+        """
+        Abstract create method.
+
+        Concrete implementations should return a new instance of the object the factory class is responsible for.
+        @param kwargs: Arguments for object creation.
+        @return: A new instance of the object the factory is responsible for.
+        """
+        pass
+

tests/creational_tests/test_factory.py

@@ -0,0 +1,63 @@
+from unittest import TestCase
+from pypatterns.creational.factory import Factory
+
+
+class FactoryTestCase(TestCase):
+    """
+    Unit testing class for the Factory class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Cat(object):
+
+            def speak(self):
+                return 'Meow'
+
+        class Dog(object):
+
+            def speak(self):
+                return 'Woof'
+
+        class CatFactory(Factory):
+
+            def create(self, **kwargs):
+                return Cat()
+
+        class DogFactory(Factory):
+
+            def create(self, **kwargs):
+                return Dog()
+
+        self.cat_class = Cat
+        self.dog_class = Dog
+        self.cat_factory = CatFactory()
+        self.dog_factory = DogFactory()
+
+    def test_not_implemented(self):
+        """
+        Test that TypeError is raised when the create method is not overridden.
+
+        @raise AssertionError: If the test fails.
+        """
+        with self.assertRaises(TypeError):
+            class EmptyFactory(Factory):
+                pass
+
+            EmptyFactory()
+
+    def test_create(self):
+        """
+        Test the create method.
+
+        @raise AssertionError: If the test fails.
+        """
+        cat = self.cat_factory.create()
+        dog = self.dog_factory.create()
+
+        self.assertEquals(self.cat_class, cat.__class__)
+        self.assertEquals(self.dog_class, dog.__class__)
+
+        self.assertEquals('Meow', cat.speak())
+        self.assertEquals('Woof', dog.speak())