I've noticed that on my local CI test platform, one of my tests is failing and I'm at a loss as to why. It's intermittent, but it fails far more often than not.

Here's the TAP output up until the failure is produced:

pi@pi-test:~/repos/rpi-wiringpi $ prove -v t/75-serial.t
t/75-serial.t .. 
ok 1 - An object of class 'RPi::Serial' isa 'RPi::Serial'
ok 2 - putc() and getc() ok
not ok 3 - puts() and gets() ok
#   Failed test 'puts() and gets() ok'
#   at t/75-serial.t line 32.
#          got: 'hello, world!'
#     expected: 'hello, world!'
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Notice how the got and expected are identical. What am I missing here?

The test is writing a string to, and then reading the string back from a serial interface. Here's the test code if it helps:

use strict;
use warnings;

use lib 't/';

use RPiTest qw(check_pin_status);
use RPi::WiringPi;
use RPi::Const qw(:all);
use Test::More;

my $mod = 'RPi::WiringPi';

if (! $ENV{RPI_SERIAL}){
    plan skip_all => "RPI_SERIAL environment variable not set\n";
}

if (! $ENV{PI_BOARD}){
    $ENV{NO_BOARD} = 1;
    plan skip_all => "Not on a Pi board\n";
}

my $pi = $mod->new;

my $s = $pi->serial("/dev/ttyS0", 115200);

isa_ok $s, 'RPi::Serial';

$s->putc(254);
is $s->getc, 254, "putc() and getc() ok";

$s->puts("hello, world!");

# FAILING TEST IS BELOW

is $s->gets(13), "hello, world!", "puts() and gets() ok";

$pi->cleanup;

check_pin_status();

done_testing();
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