use strictures;
use Test::More;
# plan test count here or use done_testing($count).

is hello_world(), "Hello world!",
    "Hello world is hello world";

# Naive test, will not catch your bug, and you have one.
cmp_ok get_number(), ">", 0,
    "get_number() returns greater than zero";

subtest "Iterate on get_number()" => sub {
    my $iterations = 10_000; # Higher confidence.
    my $ok;
    for ( 1 .. $iterations )
    {
        $ok++ if get_number() > 0;
    }
    my $msg = "get_number() returns greater than zero";
    $ok == $iterations ?
        pass($msg)
        :
        fail($msg . " - expected $iterations > 0, got $ok");

    done_testing(1);
};

done_testing(3); # <- Either "plan" or delcare test count here!

exit 0;

sub hello_world {
    "Hello world!";
}

sub get_number {
    int(rand(1000));
}

##</code><code>##

~>prove my-test.t -v
ok 1 - Hello world is hello world
ok 2 - get_number() returns greater than zero
    not ok 1 - get_number() returns greater than zero - expected 10000 > 0, got 9993
    1..1
not ok 3 - Iterate on get_number()
1..3
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/3 subtests

Test Summary Report
-------------------
/home/moo/my-test.t (Wstat: 256 Tests: 3 Failed: 1)
  Failed test:  3
Files=1, Tests=3,  0 wallclock secs ( 0.03 usr  0.01 sys +  0.03 cusr  0.00 csys =  0.07 CPU)
Result: FAIL

##</code><code>##

ok 1 - Hello world is hello world
ok 2 - get_number() returns greater than zero
    ok 1 - get_number() returns greater than zero
    1..1
ok 3 - Iterate on get_number()
1..3
ok
All tests successful.
Files=1, Tests=3,  0 wallclock secs ( 0.03 usr  0.01 sys +  0.03 cusr  0.00 csys =  0.07 CPU)
Result: PASS