RED: Test exposing missing feature - ignore numbers > 1000

- Test expects '2,1001' to return 2 (1001 ignored)
- Currently returns 1003 (includes all numbers)
- Feature not implemented yet
- Expected: <2>, Actual: <1003>

test/string_calculator_test.dart

@@ -32,5 +32,10 @@ void main() {
       expect(calculator.add('//;\n1;2'), equals(3));
       expect(calculator.add('//|\n10|20|30'), equals(60));
     });
+
+    test('numbers greater than 1000 are ignored', () {
+      expect(calculator.add('2,1001'), equals(2));
+      expect(calculator.add('1000,1001,2'), equals(1002));
+    });
   });
 }