--- /dev/null
+<?php
+
+/*
+ * This file is part of the Behat.
+ * (c) Konstantin Kudryashov <ever.zet@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Behat\Testwork\Output\Node\EventListener;
+
+use Behat\Testwork\Output\Formatter;
+use Symfony\Component\EventDispatcher\Event;
+
+/**
+ * Used to define formatter event listeners.
+ *
+ * @author Konstantin Kudryashov <ever.zet@gmail.com>
+ */
+interface EventListener
+{
+ /**
+ * Notifies listener about an event.
+ *
+ * @param Formatter $formatter
+ * @param Event $event
+ * @param string $eventName
+ */
+ public function listenEvent(Formatter $formatter, Event $event, $eventName);
+}