Plack-Test-Agent is a project mainly written in Perl, it's free.
Object oriented agent for testing PSGI and Plack components
=head1 Plack::Test::Agent
This experimental distribution is an object oriented version of Plack::Test. Its name may change. It may prove to have been a silly idea. Use it if you like, and please give feedback if you want to continue to use it.
See Lhttp://www.modernperlbooks.com/mt/2011/09/placktest-and-great-test-interfaces.html and Lhttps://github.com/miyagawa/Plack/issues/180 for discussion.