ngds/common/tests/standalone/paystack-webhook-signature.php

<?php

require __DIR__ . '/../../helpers/PayStack.php';

use common\helpers\PayStack;

$body = '{"event":"charge.success","data":{"reference":"OS123"}}';
$secret = 'standalone-test-secret';
$signature = hash_hmac('sha512', $body, $secret);
$checks = [
    'accepts the matching SHA512 signature' => PayStack::verifyWebhookSignature($body, $signature, $secret),
    'rejects a different signature' => !PayStack::verifyWebhookSignature($body, str_repeat('0', 128), $secret),
    'rejects an empty signature' => !PayStack::verifyWebhookSignature($body, '', $secret),
    'signature binds to the raw request body' => !PayStack::verifyWebhookSignature($body . ' ', $signature, $secret),
];

foreach ($checks as $description => $passed) {
    if (!$passed) {
        fwrite(STDERR, "FAIL: {$description}\n");
        exit(1);
    }
}

echo 'PASS: ' . count($checks) . " PayStack signature checks\n";