At least, until now. I made a small plugin, which connects Mech with the great HTML::Display package, which is makes it easy to display a Mech HTML page in a local browser.
I usually use Mech over an 'ssh' connection, so what's "local" to Mechanize is usually not my desktop where there's a graphical browser running. So in the example, I show how to use the great console browser, w3m, for display. It (sort of) renders tables, which is usually enough to at least give me an idea of what went wrong. Here's how I might use it with Test::WWW::Mechanize:
$mech->get_ok($url) || $mech->display();
If this test fails, I'll see the result in the browser. I don't always leave the calls to "display()" in the code when I'm done, since this wouldn't make sense in the content of a smokebot.
See WWW::Mechanize::Plugin::Display on CPAN.