App::Cmd::Tester provides a useful scaffold for testing applications, but it
is unable to capture output generated from any external subprograms that are
invoked from the application.
This subclass uses an alternate mechanism for capturing output
(Capture::Tiny) that does capture from external programs, with one
It is not possible to capture externally from both STDOUT and STDERR while
also having appropriately interleaved combined output. Therefore, the
output from this subclass simply concatenates the two.
You can still use output for testing if there is any output at all or for
testing if something appeared in either output stream, but you cant rely on
the ordering being correct between lines to STDOUT and lines to STDERR.