# foo.t
use strict;
use warnings;

use Test::More; # don't put a plan here

use t::Helper qw/multi_test/; # i.e. t/Helper.pm

my @cases = (
    {
        label => "describe this case",
        input => "data to operate on",
        output => "expected result",
    },
    # ... repeat as needed ...
);

# set plan after populating @cases

my $tests_per_case = 2;
plan tests => 1 + $tests_per_case * @cases; 

# start testing here
require_ok( "Some::Object" );

for my $case ( @cases ) {
    my $obj = Some::Object->new;
    multi_test( $obj, $case );
}