diff --git a/comtypes/test/test_GUID.py b/comtypes/test/test_GUID.py
index ef8ae1e6..c1effd26 100644
--- a/comtypes/test/test_GUID.py
+++ b/comtypes/test/test_GUID.py
@@ -1,34 +1,55 @@
-import os
 import unittest
 from comtypes import GUID
 
 
 class Test(unittest.TestCase):
-    def test(self):
+    def test_GUID_null(self):
         self.assertEqual(GUID(), GUID())
+        self.assertEqual(
+            str(GUID()),
+            "{00000000-0000-0000-0000-000000000000}",
+        )
+
+    def test_dunder_eq(self):
         self.assertEqual(
             GUID("{00000000-0000-0000-C000-000000000046}"),
             GUID("{00000000-0000-0000-C000-000000000046}"),
         )
 
+    def test_duner_str(self):
         self.assertEqual(
             str(GUID("{0002DF01-0000-0000-C000-000000000046}")),
             "{0002DF01-0000-0000-C000-000000000046}",
         )
+
+    def test_dunder_repr(self):
         self.assertEqual(
             repr(GUID("{0002DF01-0000-0000-C000-000000000046}")),
             'GUID("{0002DF01-0000-0000-C000-000000000046}")',
         )
 
+    def test_invalid_constructor_arg(self):
         self.assertRaises(WindowsError, GUID, "abc")
+
+    def test_from_progid(self):
+        self.assertEqual(
+            GUID.from_progid("Scripting.FileSystemObject"),
+            GUID("{0D43FE01-F093-11CF-8940-00A0C9054228}"),
+        )
         self.assertRaises(WindowsError, GUID.from_progid, "abc")
 
+    def test_as_progid(self):
+        self.assertEqual(
+            GUID("{0D43FE01-F093-11CF-8940-00A0C9054228}").as_progid(),
+            "Scripting.FileSystemObject",
+        )
         self.assertRaises(
             WindowsError,
             lambda guid: guid.as_progid(),
             GUID("{00000000-0000-0000-C000-000000000046}"),
         )
 
+    def test_create_new(self):
         self.assertNotEqual(GUID.create_new(), GUID.create_new())