diff --git a/tests/test_ifs_sim.py b/tests/test_ifs_sim.py
index 3969bd4a9716a8fd212978473eb4991b41e41bf9..9c6319e1768754df5cc0e4506d05ae21d0eaab96 100644
--- a/tests/test_ifs_sim.py
+++ b/tests/test_ifs_sim.py
@@ -31,7 +31,7 @@ class TestDemoFunction(unittest.TestCase):
         This case aims to test whether the demo function returns `1` if input is `None`.
         """
         # demo function test
-        dir_path=os.path.join(os.environ['UNIT_TEST_DATA_ROOT'],'ifs_sim')
+        dir_path=os.path.join(os.environ['UNIT_TEST_DATA_ROOT'],'ifs_sim/')
         
         print(dir_path)