Add test.

module/VuFind/tests/unit-tests/src/VuFindTest/AjaxHandler/RecommendTest.php

+<?php
+/**
+ * Recommend test class.
+ *
+ * PHP version 7
+ *
+ * Copyright (C) Villanova University 2018.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category VuFind
+ * @package  Tests
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org Main Page
+ */
+namespace VuFindTest\AjaxHandler;
+
+use VuFind\AjaxHandler\Recommend;
+
+/**
+ * Recommend test class.
+ *
+ * @category VuFind
+ * @package  Tests
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org Main Page
+ */
+class RecommendTest extends \VuFindTest\Unit\AjaxHandlerTest
+{
+    /**
+     * Test the AJAX handler's basic response.
+     *
+     * @return void
+     */
+    public function testResponse()
+    {
+        $ss = $this->getMockService('VuFind\Session\Settings', ['disableWrite']);
+        $ss->expects($this->once())->method('disableWrite');
+        $mockPlugin = $this->getMockService('VuFind\Recommend\RecommendInterface');
+        $rm = $this->getMockService('VuFind\Recommend\PluginManager', ['get']);
+        $rm->expects($this->once())->method('get')->with($this->equalTo('foo'))
+            ->will($this->returnValue($mockPlugin));
+        $r = $this->getMockService('VuFind\Search\Solr\Results');
+        $viewHelper = $this->getMockService('VuFind\View\Helper\Root\Recommend');
+        $view = $this
+            ->getMockService('Zend\View\Renderer\PhpRenderer', ['plugin']);
+        $view->expects($this->once())->method('plugin')
+            ->with($this->equalTo('recommend'))
+            ->will($this->returnValue($viewHelper));
+        $handler = new Recommend($ss, $rm, $r, $view);
+        $params = $this->getParamsHelper(['mod' => 'foo']);
+        $this->assertEquals([null, 'OK'], $handler->handleRequest($params));
+    }
+}