I've looked at:

  man Module::Build::Authoring
  man Module::Build::Cookbook
[download]

.but still am not sure of the best place in  Build.PL to list modules that are used only in t/*.t. In my *.t files non standard modules are guarded like:

use Test::More;  # in Build.PL::build_requires
eval 'use Test::Do::Funky:Chicken;'
if ($@){
  plan skip_all => 'Test::Funky::Chicken needed';
}else{
  plan tests => 99;
}
[download]

I am tending toward the recommends section.

Advice ?

UPDATE: fixed eval per ysth kind and helpful advice.