implemented strategy pattern

pypatterns/behavioral/strategy.py

@@ -0,0 +1,17 @@
+from abc import ABCMeta, abstractmethod
+
+
+class Strategy(object):
+    """
+    An abstract Strategy class.
+    All strategies should inherit this class.
+    """
+    __metaclass__ = ABCMeta
+
+    @abstractmethod
+    def __call__(self, *args, **kwargs):
+        """
+        Abstract method that must be overridden.
+        The overridden method should execute the classes strategy.
+        """
+        pass

tests/behavioral_tests/test_strategy.py

@@ -0,0 +1,66 @@
+from unittest import TestCase
+from pypatterns.behavioral.strategy import Strategy
+
+
+class StategyTestCase(TestCase):
+    """
+    Unit testing class for the Strategy pattern.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class AddStrategy(Strategy):
+
+            def __call__(self, a, b):
+                return a + b
+
+        class SubtractStrategy(Strategy):
+
+            def __call__(self, a, b):
+                return a - b
+
+        class Solver(object):
+
+            def __init__(self, strategy):
+                self.strategy = strategy
+
+            def solve(self, a, b):
+                return self.strategy(a, b)
+
+        self.add_class = AddStrategy
+        self.subtract_class = SubtractStrategy
+        self.solver_class = Solver
+
+    def test_add_strategy(self):
+        """
+        Test the add strategy.
+
+        @raise AssertionError: If the test fails.
+        """
+        solver = self.solver_class(self.add_class())
+
+        self.assertEquals(15, solver.solve(5, 10))
+
+    def test_subtract_strategy(self):
+        """
+        Test the subtract strategy.
+
+        @raise AssertionError: If the test fails.
+        """
+        solver = self.solver_class(self.subtract_class())
+
+        self.assertEquals(10, solver.solve(100, 90))
+
+    def test_switch_strategies(self):
+        """
+        Test changing out strategies.
+
+        @raise AssertionError: If the test fails.
+        """
+        solver = self.solver_class(self.add_class())
+        self.assertEquals(5, solver.solve(2, 3))
+
+        solver.strategy = self.subtract_class()
+        self.assertEquals(-1, solver.solve(2, 3))
+