Install libplack-middleware-test-stashwarnings-perl by entering the following commands in the terminal:
sudo apt update sudo apt install libplack-middleware-test-stashwarnings-perl
module for testing plack application warnings
Plack::Middleware::Test::StashWarnings is a Plack middleware component to record warnings generated by your application so that you can test them to make sure your application complains about the right things. . The warnings generated by your application are available at a special URL (/__test_warnings), encoded with Storable/nfreeze. So using Test::WWW::Mechanize you can just get that URL and Storable/thaw its content.