Add unit test for generated IEnum (enthought#468) (enthought#471)

* unit test for generated IEnum (enthought#468)

* change enum_test to a non-empty IEnum

* improved checks and clarity

* apply requested changes

Co-authored-by: jonschz <[email protected]>
(cherry picked from commit e1ee6f0)

Author: jonschz

comtypes/test/test_ienum.py

@@ -0,0 +1,29 @@
+import contextlib
+import unittest as ut
+
+from ctypes import POINTER
+from comtypes import GUID
+import comtypes.client
+
+
+class Test_IEnum(ut.TestCase):
+    def test_ienum(self):
+        with contextlib.redirect_stdout(None):  # supress warnings, see test_client.py
+            comtypes.client.GetModule("msvidctl.dll")
+        from comtypes.gen import MSVidCtlLib as vidlib
+
+        CLSID_AviSplitter = GUID("{1b544c20-fd0b-11ce-8c63-00aa0044b51e}")
+
+        avisplitter = comtypes.client.CreateObject(
+            CLSID_AviSplitter,
+            interface=vidlib.IBaseFilter,
+        )
+        pinEnum = avisplitter.EnumPins()
+        self.assertIsInstance(pinEnum, POINTER(vidlib.IEnumPins))
+        # make sure pinEnum is iterable and non-empty
+        pins = list(pinEnum)
+        self.assertGreater(len(pins), 0)
+
+
+if __name__ == "__main__":
+    ut.main()