I have some huge test suites that have a number of needed modules that dwarfs that of the software itself.
I mean the software installs in seconds, but if I force-required all of the modules needed to test the entire application at the level I need it tested before release, the install can take over 30 minutes (or longer).
What I do is make the tests optional, if the needed modules for testing aren't installed. If a test has all needed modules, they run. I can have many of these scenarios in a single test file sometimes.
I ensure that ALL tests are run on several versions of Perl locally (with pre-installed test modules), and also put into my CI configuration the cpanm install commands for all of the test modules, so that they run on various Perls on several OSs there as well.
The Makefile.PL that is uploaded to the CPAN contains only the distributions that the software needs to run, plus any basic ones that the build (ie. test) phase needs. By running all tests locally as well as CI, I can be quite reasonably sure that the software will work for my users too.
The only time I won't bypass an install of a large module or collection of modules used for testing, is if the part of code that's being tested is in the critical path, that is it is a critical piece of functionality that if tests fail, the software may be rendered inoperable, or worse. I need these tests to pass on each client device, not just on a selection of Perls and OSs upstream somewhere.