add PingHandler Test

tests/AppTest/Handler/PingHandlerTest.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace AppTest\Handler;
+
+use App\Handler\PingHandler;
+use Laminas\Diactoros\Response\JsonResponse;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ServerRequestInterface;
+
+use function json_decode;
+use function property_exists;
+
+use const JSON_THROW_ON_ERROR;
+
+class PingHandlerTest extends TestCase
+{
+    public function testResponse(): void
+    {
+        $pingHandler = new PingHandler();
+        $response    = $pingHandler->handle(
+            $this->createMock(ServerRequestInterface::class)
+        );
+
+        $json = json_decode((string) $response->getBody(), null, 512, JSON_THROW_ON_ERROR);
+
+        self::assertInstanceOf(JsonResponse::class, $response);
+        self::assertTrue(property_exists($json, 'ack') && $json->ack !== null);
+    }
+}