add test for http publisher

Author: miladrahimi

src/Services/HttpPublisher.php

@@ -25,6 +25,8 @@ public function publish($content): void
             fwrite($output, $content->getBody());
         } elseif (is_scalar($content)) {
             fwrite($output, $content);
+        } elseif ($content === null) {
+            fwrite($output, '');
         } else {
             fwrite($output, json_encode($content));
         }

tests/Services/HttpPublisherTest.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace MiladRahimi\PhpRouter\Tests\Services;
+
+use Laminas\Diactoros\Response\JsonResponse;
+use MiladRahimi\PhpRouter\Router;
+use MiladRahimi\PhpRouter\Tests\TestCase;
+use Throwable;
+
+class HttpPublisherTest extends TestCase
+{
+    /**
+     * @throws Throwable
+     */
+    public function test_publish_a_string_response()
+    {
+        ob_start();
+
+        $router = Router::create();
+        $router->get('/', function () {
+            return 'Hello!';
+        });
+        $router->dispatch();
+
+        $this->assertEquals('Hello!', ob_get_clean());
+    }
+
+    /**
+     * @throws Throwable
+     */
+    public function test_publish_a_empty_response()
+    {
+        ob_start();
+
+        $router = Router::create();
+        $router->get('/', function () {
+            //
+        });
+        $router->dispatch();
+
+        $this->assertEmpty(ob_get_clean());
+    }
+
+    /**
+     * @throws Throwable
+     */
+    public function test_publish_a_array_response()
+    {
+        ob_start();
+
+        $router = Router::create();
+        $router->get('/', function () {
+            return ['a', 'b', 'c'];
+        });
+        $router->dispatch();
+
+        $this->assertEquals('["a","b","c"]', ob_get_clean());
+    }
+}