diff --git a/Observer.py b/Observer.py
index 7716a60..dc40dd3 100644
--- a/Observer.py
+++ b/Observer.py
@@ -81,21 +81,20 @@ class Observable():
         Adds observer to notification list.
         """
         # FIXME: Check name unique
-        try:
-            if not(observer in self.obs_collection):
-                self.obs_collection.append(observer)
-                #print "%s added to collection" % (str(observer))
-            else:
-                pass
-                #print "%s already in collection" % (str(observer))
+        if not isinstance(observer, Observer):
+            raise TypeError("Subscriber must be Observer")
 
-        except TypeError:
-            print "Failed to add %s" % (str(observer))
+        if (observer in self.obs_collection):
+            raise ValueError("Observer already subscribed")
+        self.obs_collection.append(observer)
 
     def unsubscribe(self, observer):
         """
         Removes observer from notification list.
         """
+        if not isinstance(observer, Observer):
+            raise TypeError("Unsubscriber must be Observer")
+
         try:
             if observer in self.obs_collection:
                 self.obs_collection.remove(observer)
@@ -107,7 +106,7 @@ class Observable():
         except TypeError:
             print "Failed to remove %s" % (str(observer))
 
-    def notify(self, mess):
+    def __notify(self, mess):
         """
         Sends notification message to all subscribed observer
         """
@@ -120,6 +119,8 @@ class Observable():
         Shall be used for automatic polling.
         Sets current Observable value and notifies update to subscribers.
         """
+        if not isinstance(val, str):
+            raise TypeError("Expected string for message")
+
         self.message = val
-        if val != None:
-            self.notify(self.message)
+        self.__notify(self.message)
diff --git a/testObserver.py b/testObserver.py
index 67c34a1..b65359e 100644
--- a/testObserver.py
+++ b/testObserver.py
@@ -59,7 +59,7 @@ class TestObserver(unittest.TestCase):
         self.assertEquals(str(self.myObserver1), self.name1)
         self.assertRaises(TypeError, lambda: obs.Observer(42))
 
-        # tests message
+        # tests message and update
         self.assertEquals(self.myObserver1.message, self.default_mess)
         new_message = "new_message"
         self.myObserver1.update(new_message)
@@ -67,13 +67,23 @@ class TestObserver(unittest.TestCase):
         self.assertRaises(TypeError, lambda: self.myObserver1.update([4, 2]))
         self.assertRaises(TypeError, lambda: self.myObserver1.update(None))
 
+    def testObservable(self):
+        self.assertRaises(TypeError, lambda: self.myObservable.set_val(42))
+        self.assertRaises(TypeError, lambda: self.myObservable.set_val(None))
+
+        val = "luke"
+        self.myObservable.set_val(val)
+        self.assertEquals(val, self.myObservable.message)
 
     def testSubscribe(self):
+        self.assertEquals(len(self.myObservable.obs_collection), 0)
+        self.assertRaises(TypeError, lambda: self.myObservable.subscribe(42))
 
+        self.myObservable.subscribe(self.myObserver1)
+        self.assertRaises(ValueError, lambda: self.myObservable.subscribe(self.myObserver1))  # already there
+        self.myObservable.subscribe(self.myObserver2)
 
-        pass
-
-
+        self.assertEquals(len(self.myObservable.obs_collection), 2)
 
     def testUnsubscribe(self):
         pass
@@ -85,33 +95,5 @@ class TestObserver(unittest.TestCase):
         pass
 
 
-
-
-
-
-
-
-
-
-
-
-
-
-
 if __name__ == '__main__':
-    unittest.main()
-    # a = Observer("riri")
-    # b = Observer("fifi")
-    # c = Observer("loulou")
-
-    # d = Observable()
-
-    # d.subscribe(a)
-    # d.subscribe(b)
-    # d.subscribe(b)
-    # d.subscribe(c)
-
-    # d.unsubscribe(b)
-
-    # d.set_val(3)
-    # d.set_val()
\ No newline at end of file
+    unittest.main()
\ No newline at end of file