improved proxy implementation.

proxy must now contain all public methods that the subject has.

pypatterns/structural/proxy.py

@@ -1,4 +1,7 @@
-class Proxy(object):
+from abc import ABCMeta
+
+
+class Proxy(object, metaclass=ABCMeta):
     """
     Base Proxy class as part of the Proxy design pattern.
     """
@@ -9,6 +12,22 @@ class Proxy(object):
         @param subject: The real subject this proxy calls upon.
         """
         self._subject = subject
+        self._validate()
+
+    def _validate(self):
+        """
+        Validate that the subject and this proxy follow the same interface.
+
+        @raise AttributeError: If the subject and this proxy do not follow the same interface.
+        """
+        for attr in dir(self._subject):
+            if attr.startswith('_') or attr.startswith('__'):
+                continue
+
+            elif not callable(getattr(self._subject, attr, None)) or not callable(getattr(self, attr, None)):
+                raise AttributeError('Subject and Proxy must follow same interface')
+
+
 
 
 

tests/structural_tests/test_proxy.py

@@ -20,6 +20,15 @@ class ProxyTestCase(TestCase):
             def __init__(self, age):
                 self.age = age
 
+        self.car = Car()
+        self.driver = Driver(17)
+
+    def test_valid_proxy(self):
+        """
+        Test a Proxy class following the same interface as the subject.
+
+        @raise AssertionError: If the test fails.
+        """
         class ProxyCar(Proxy):
 
             def __init__(self, subject, driver):
@@ -32,14 +41,25 @@ class ProxyTestCase(TestCase):
                 else:
                     return 'Driver is too young to drive'
 
-        self.proxy = ProxyCar(Car(), Driver(17))
+        try:
+            proxy = ProxyCar(self.car, self.driver)
+        except AttributeError:
+            raise AssertionError()
+        else:
+            self.assertEqual('drive car', proxy.drive_car())
+            proxy.driver.age = 15
+            self.assertEqual('Driver is too young to drive', proxy.drive_car())
 
-    def test_drive_car(self):
+    def test_invalid_proxy(self):
         """
-        Test the proxy with the drive car method.
+        Test a Proxy class that is not following the same interface as the subject.
 
         @raise AssertionError: If the test fails.
         """
-        self.assertEqual('drive car', self.proxy.drive_car())
+        class ProxyCar(Proxy):
-        self.proxy.driver.age = 15
+
-        self.assertEqual('Driver is too young to drive', self.proxy.drive_car())
+            def __init__(self, subject, driver):
+                super().__init__(subject)
+                self.driver = driver
+
+        self.assertRaises(AttributeError, lambda: ProxyCar(self.car, self.driver))