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/ListUsersControllerTest.php

@@ -0,0 +1,40 @@
+<?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\ListUsersController;
+
+class ListUsersControllerTest extends ApiControllerTestCase
+{
+    protected $controller = ListUsersController::class;
+
+    /**
+     * @test
+     * @expectedException \Flarum\User\Exception\PermissionDeniedException
+     */
+    public function disallows_index_for_guest()
+    {
+        $this->callWith();
+    }
+
+    /**
+     * @test
+     */
+    public function shows_index_for_admin()
+    {
+        $this->actor = $this->getAdminUser();
+
+        $response = $this->callWith();
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+}