diff --git a/tests/test_file.py b/tests/test_file.py
new file mode 100644
index 0000000000000000000000000000000000000000..940557824d48a3758eb4eed1a1e6dc5ae2c8b90c
--- /dev/null
+++ b/tests/test_file.py
@@ -0,0 +1,9 @@
+import unittest
+from csst_common import File
+
+
+class TestFile(unittest.TestCase):
+    def test_parameterized_module_decorator(self):
+        f = File("/path/to/file.fits")
+        self.assertEqual(f.switch_extension(".cat"), "/path/to/file.cat")
+        self.assertEqual(f.switch_extension("img.cat"), "/path/to/file_img.cat")