diff --git a/counter.py b/counter.py
index 61fb094fd36601ec8b89ecb0ed27d4ecdaaa3ddc..73ac0959c513243642e6cde168bd0f6fd59e8b9a 100644
--- a/counter.py
+++ b/counter.py
@@ -11,25 +11,43 @@ class ICounter (ABC):
         pass
 
 class Counter (ICounter):
-    #def count_ED(self,s):
-    #return s.count("e")+s.count("D")
-    pass
+    def count_ED(self,s):
+        s = s.upper()
+        return s.count("D")+s.count("E")
+    
 
 class TestCounter (unittest.TestCase):
+    def setUp(self):
+        self.c = Counter()
+
     def test_count_ED_regular (self):
-        c=Counter()
-        res=c.count_ED ("Decker")
+        res=self.c.count_ED ("Decker")
         self.assertEqual(res,3)
+
     def test_count_ED_empty (self):
-        c=Counter()
-        res=c.count_ED ("")
+        res=self.c.count_ED ("")
         self.assertEqual(res,0)
+
     def test_count_ED_wo (self):
         '''Testet einen String ohne E und D'''
-        c=Counter()
-        res=c.count_ED ("Hallo")
+        res=self.c.count_ED ("Hallo")
         self.assertEqual(res,0)
-    def
+
+    def test_count_ED_insensitive(self):
+        '''Testet verschiedene Groß- und Kleinschreibungen'''
+        res=self.c.count_ED("Der Esel")
+        self.assertEqual(res, 4)
+
+    def test_count_ED_single_letter(self):
+        '''Testet Eingaben mit nur einem Buchstaben'''
+        res=self.c.count_ED("D")
+        self.assertEqual(res, 1)
+        res=self.c.count_ED("E")
+        self.assertEqual(res, 1)
+        res=self.c.count_ED("d")
+        self.assertEqual(res, 1)
+        res=self.c.count_ED("e")
+        self.assertEqual(res, 1)
 
 if __name__=="__main__":
     unittest.main()