I'm working on the testing section of the Little Plack Book. Simplified testing is a huge benefit of Plack, but Plack's flexibility is evident even in Plack::Test.

You can run your tests against a mock HTTP server with Plack::Test , but you can also run them against any server backend supported by a Plack::Handler .

If you use Plack::Test (whether directly or through something which builds on Plack::Test ), when do you use a real server backend? What are your motivations for doing so?

I've come up with "standard devops paranoia" and "testing server compliance" as two good reasons. What others exist?