# file: t/helper.pm
package t::helper;

@EXPORT = qw( run_all_tests );

use strict;
use warnings;
use base 'Exporter';
use Test::More;

sub run_all_tests {
    my ($obj, $prefix) = @_;

    diag "Starting tests for $prefix";
    
    isa_ok( $obj, "Parent::Class", "$prefix: object isa Parent::Class" );

    ok( $obj->true(), "$prefix: true() is true" );

    # more tests ...
}

1;

##</code><code>##

# file: t/001.t
use Test::More 'no_plan';
use t::helper;

my @cases = ( 
    Parent::Class->new(), 
    Sub::Class->new(),
);

for my $o ( @objs ) {
    run_all_tests( $o, ref $o );
}