Test failures are an indicator of either a bug or a problem with your system. In most cases, the latter should also be classified as a bug, unless the module author has documented that it should not, or is not intended to work on platform X.

As a first port of call, check the README or INSTALL. Just to make sure that this is a normal CPAN install.

Secondly, check CPAN testers to see what install problems, if any, have been encountered by the smoke testers. This is linked from the search.cpan.org module page.

Finally, check RT (also linked from the same place) to see if anyone else has reported this problem. If this is not the case, report the problem yourself to RT, which will result in the module author getting an email, and you have a ticket number that you can use to track progress.

As to whether to proceed installing a module with failing tests, "Caveat updator"; on your conscience be it. If you can work out what the tests/module _should_ be doing, stick a patch into the RT ticket; the author will in most cases be grateful.