Rename API tests for more consistency

I could not come up with a noun for the new "UpdateTest" for users, so
this is easier in terms of consistency.

tests/integration/api/posts/CreateTest.php

@@ -0,0 +1,67 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\integration\api\posts;
+
+use Carbon\Carbon;
+use Flarum\Tests\integration\RetrievesAuthorizedUsers;
+use Flarum\Tests\integration\TestCase;
+
+class CreateTest extends TestCase
+{
+    use RetrievesAuthorizedUsers;
+
+    public function setUp()
+    {
+        parent::setUp();
+
+        $this->prepareDatabase([
+            'discussions' => [
+                ['id' => 1, 'title' => __CLASS__, 'created_at' => Carbon::now()->toDateTimeString(), 'user_id' => 2],
+            ],
+            'posts' => [],
+            'users' => [
+                $this->normalUser(),
+            ],
+            'groups' => [
+                $this->memberGroup(),
+            ],
+            'group_user' => [
+                ['user_id' => 2, 'group_id' => 3],
+            ],
+            'group_permission' => [
+                ['permission' => 'viewDiscussions', 'group_id' => 3],
+            ]
+        ]);
+    }
+
+    /**
+     * @test
+     */
+    public function can_create_reply()
+    {
+        $response = $this->send(
+            $this->request('POST', '/api/posts', [
+                'authenticatedAs' => 2,
+                'json' => [
+                    'data' => [
+                        'attributes' => [
+                            'content' => 'reply with predetermined content for automated testing - too-obscure',
+                        ],
+                        'relationships' => [
+                            'discussion' => ['data' => ['id' => 1]],
+                        ],
+                    ],
+                ],
+            ])
+        );
+
+        $this->assertEquals(201, $response->getStatusCode());
+    }
+}