diff --git a/scrapy/tests/test_engine.py b/scrapy/tests/test_engine.py
index 160193d3f..13af7a8c8 100644
--- a/scrapy/tests/test_engine.py
+++ b/scrapy/tests/test_engine.py
@@ -1,3 +1,15 @@
+"""
+Scrapy engine tests
+
+This starts a testing web server (using twisted.server.Site) and then crawls it
+with the Scrapy crawler.
+
+To view the testing web server in a brwoser you can run start it by running
+this module with the ``runserver`` argument::
+
+    python test_engine.py runserver
+"""
+
 import sys, os, re, urlparse
 
 from twisted.internet import reactor, defer