test_ntpath and test_posixpath failed if sys.getfilesystemencoding()=='mbcs'

Author: native-api

Lib/test/support/__init__.py

@@ -844,7 +844,8 @@ def dec(*args, **kwargs):
     '\u20AC',
 ):
     try:
-        os.fsdecode(os.fsencode(character))
+        if os.fsdecode(os.fsencode(character)) != character:
+            raise UnicodeError
     except UnicodeError:
         pass
     else: