This modules causes any warnings produced by test scripts to be
captured and stored. It automatically adds an extra test that will run
when your script ends to check that there were no warnings. If there
were any warings, the test will give a "not ok" and diagnostics of
where, when and what the warning was, including a stack trace of what
was going on when the it occurred.

WWW: http://search.cpan.org/dist/Test-NoWarnings/