Add fake userkey manager for testing

tests/fake_userkey_manager.php

@@ -0,0 +1,37 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Fake userkey manager for testing.
+ *
+ * @package    auth_userkey
+ * @copyright  2016 Dmitrii Metelkin (dmitriim@catalyst-au.net)
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace auth_userkey;
+
+
+class fake_userkey_manager implements userkey_manager_interface {
+
+    public function create_key() {
+        return 'FaKeKeyFoRtEsTiNg';
+    }
+
+    public function delete_key() {
+
+    }
+}