How common is a single failed test? Pretty common. Some authors don't even intend their tests to work on every system. However, CGI-Session is one where I expect the authors did intend the tests to work for end users, and if you file a bug through the bug reporting link on CPAN this will most likely get fixed. It probably just needs to skip this test if DB_File is not functional on the system. It's not unusual for a few tests to break on certain platforms that are very different from what the author has access to. A good bug report will help take care of it.