diff --git a/src/test/py/test_primitive_calculations.py b/src/test/py/test_primitive_calculations.py
index 211610f..a9d77c9 100644
--- a/src/test/py/test_primitive_calculations.py
+++ b/src/test/py/test_primitive_calculations.py
@@ -12,6 +12,9 @@ class primitive_calculations(unittest.TestCase):
     def test_add_5_plus_5_equals_10(self):
         self.assertEqual(add(5, 5), 10)
 
+    def test_add_minus_5_plus_minus_5_equals_10(self):
+        self.assertEqual(add(-5, -5), -10)
+
 
 if __name__ == "__main__":
     unittest.main()