I have an application written in CGI::Application, and CGI::Application has an offline mode that directly returns a string instead of printing it - and then I write tests against that returned string (or rather, I parse the response into headers and body, and test the headers and the body). Test::HTML::Content is still crude and not yet ported to XPath syntax, but it might help already.

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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