The 'make test' target in ExtUtils::MakeMaker calls the test suite via

test_harness(0, 'blib/lib', 'blib/arch')
[download]

making sure that @INC is set correctly in */*.t scripts called subsequently.

But what if one of these scripts in t/*.t calls another script (e.g. a bin script that's part of the module distro and needs to be tested), how do I make sure that it gets called with the correct -I setting, in order to find my yet-to-be-installed modules? I was thinking

system( $^X, "-Iblib/lib", "path/scriptname" );
[download]

but setting -I manually to "blib/lib" breaks encapsulation, Test::Harness should provide a setting for that, but I can't find it. Any pointers?