private function create_forum() {
        global $DB;

        $discussions = self::$paramforumdiscussions[$this->size];
        $posts = self::$paramforumposts[$this->size];
        $totalposts = $discussions * $posts;

        $this->log('createforum', $totalposts, true);

        // Create empty forum.
        $forumgenerator = $this->generator->get_plugin_generator('mod_forum');
        $record = array('course' => $this->course,
                'name' => get_string('pluginname', 'forum'));
        $options = array('section' => 0);
        $forum = $forumgenerator->create_instance($record, $options);

        // Add discussions and posts.
        $sofar = 0;
        for ($i = 0; $i < $discussions; $i++) {
            $record = array('forum' => $forum->id, 'course' => $this->course->id,
                    'userid' => $this->get_target_user());
            $discussion = $forumgenerator->create_discussion($record);
            $parentid = $DB->get_field('forum_posts', 'id', array('discussion' => $discussion->id), MUST_EXIST);
            $sofar++;
            for ($j = 0; $j < $posts - 1; $j++, $sofar++) {
                $record = array('discussion' => $discussion->id,
                        'userid' => $this->get_target_user(), 'parent' => $parentid);
                $forumgenerator->create_post($record);
                $this->dot($sofar, $totalposts);
            }
        }

        $this->end_log();
    }