Move integration tests to separate directory

Again, we do all of this to prepare for creating "real" test suites for
each type of tests.

tests/integration/api/Controller/CreatePostControllerTest.php

@@ -0,0 +1,52 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\integration\api\Controller;
+
+use Flarum\Api\Controller\CreatePostController;
+use Flarum\Discussion\Discussion;
+use Illuminate\Support\Arr;
+
+class CreatePostControllerTest extends ApiControllerTestCase
+{
+    protected $controller = CreatePostController::class;
+
+    protected $data = [
+        'content' => 'reply with predetermined content for automated testing - too-obscure'
+    ];
+
+    /**
+     * @var Discussion
+     */
+    protected $discussion;
+
+    protected function init()
+    {
+        $this->actor = $this->getNormalUser();
+        $this->discussion = Discussion::start(__CLASS__, $this->actor);
+
+        $this->discussion->save();
+    }
+
+    /**
+     * @test
+     */
+    public function can_create_reply()
+    {
+        $body = [];
+        Arr::set($body, 'data.attributes', $this->data);
+        Arr::set($body, 'data.relationships.discussion.data.id', $this->discussion->id);
+
+        $response = $this->callWith($body);
+
+        $this->assertEquals(201, $response->getStatusCode());
+    }
+}