test successful but function maybe useless

stringCalculator.py

@@ -28,6 +28,10 @@ class StringCalculator(IStringCalculator):
         '''Zahlen mit Kommas werden aufgeteilt'''
         list = numbers.split(",")
 
+        '''Nur 2 Werte sollen miteinander multipliziert werden'''
+        if len(list)>2:
+            return "only two numbers allowed"
+
         '''Konvertirung von Strings zu Integer'''
         result = 0
         for num in list:
@@ -56,5 +60,9 @@ class TestStringCalculator(unittest.TestCase):
         res = self.c.add("0,5")
         self.assertEqual(res, 5)
 
+    def test_addingThreeNumbers(self):
+        res = self.c.add("1,2,3")
+        self.assertEqual(res, "only two numbers allowed")
+
 if __name__ == "__main__":
     unittest.main()
\ No newline at end of file