There is no generally accepted naming and location agreement for integration tests that I know about in Perl.
From my observations, most people put everything under t /.
Some polls are divided into subdirectories under t / (so you may have integration tests in a separate t / integration / directory).
Some people use a file prefix (so you might have integration tests called "I-whatever.t").
Some people don't care - and just drop everything into the same directory.
I sometimes saw people separate a group of tests from a separate directory at the same level as "t /", but this was usually for tests that usually do not run (for example, author-specific tests for CPAN-tus) than for integration with unit).