diff --git a/string_calculator b/string_calculator
new file mode 100644
index 0000000000000000000000000000000000000000..46ec5a923684b74910b40c7337fb66682e8f9b20
--- /dev/null
+++ b/string_calculator
@@ -0,0 +1,33 @@
+import unittest
+
+class StringCalculator:
+    def add(self, numbers: str) -> int:
+        if not numbers:
+            return 0
+
+        number_list = [int(n) for n in numbers.split(",") if n.strip() != ""]
+        return sum(number_list)
+
+class TestStringCalculator(unittest.TestCase):
+    """Test suite for the StringCalculator class."""
+
+    def setUp(self):
+        """neue Instanz des StringCalculators vor jedem Test """
+        self.calculator = StringCalculator()
+    def test_empty_string_returns_zero(self):
+        
+        """Test: Leerer String soll 0 ergeben"""
+        self.assertEqual(self.calculator.add(""), 0)
+
+    def test_single_number_returns_value(self):
+        
+        """Test: Ein einzelner Wert soll zurückgegeben werden"""
+        self.assertEqual(self.calculator.add("1"), 1)
+
+    def test_two_numbers_return_sum(self):
+       
+        """Test: Zwei Zahlen sollen summiert werden"""
+        self.assertEqual(self.calculator.add("1,2"), 3)
+    
+if __name__=='__main__':
+    unittest.main()
\ No newline at end of file