This is not a very exciting example, but I tried this for testing a wacky sort program in C (but the language doesn't matter at all, as the program is just called via backticks):

use List::Util 'shuffle';
use Test::More;
 
my $N = 20; # number of tests; max list length
my $M = 20; # random number range
 
plan tests => $N;
for (1 .. $N) {
    my @a = shuffle map { int(rand($M)) } 1 .. $N;
    my @got = map {chomp; $_} `./mysort <<EOF
        @a
        -1
EOF`;
    my @s = sort { $a <=> $b } @a;
    is_deeply(\@got, \@s)
        or diag "@got\n@s\n";
 
}
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