diff --git a/tests/coverage_server.py b/tests/coverage_server.py
index 4bb53df..7a135c5 100644
--- a/tests/coverage_server.py
+++ b/tests/coverage_server.py
@@ -1,23 +1,23 @@
 #!/usr/bin/env python
 
-import tornado.ioloop
-import tornado.web
-import urllib
+if __name__ == '__main__':
+    import tornado.ioloop
+    import tornado.web
+    import urllib
 
+    class MainHandler(tornado.web.RequestHandler):
+        def get(self):
+            with open('/tmp/shadowsocks-coverage', 'rb') as f:
+                coverage = f.read().strip()
+                self.redirect(('https://img.shields.io/badge/'
+                               'coverage-%s-brightgreen.svg'
+                               '?style=flat') %
+                              urllib.quote(coverage))
 
-class MainHandler(tornado.web.RequestHandler):
-    def get(self):
-        with open('/tmp/shadowsocks-coverage', 'rb') as f:
-            coverage = f.read().strip()
-            self.redirect(('https://img.shields.io/badge/'
-                           'coverage-%s-brightgreen.svg'
-                           '?style=flat') %
-                          urllib.quote(coverage))
+    application = tornado.web.Application([
+        (r"/shadowsocks", MainHandler),
+    ])
 
-application = tornado.web.Application([
-    (r"/shadowsocks", MainHandler),
-])
-
-if __name__ == "__main__":
-    application.listen(8888, address='127.0.0.1')
-    tornado.ioloop.IOLoop.instance().start()
+    if __name__ == "__main__":
+        application.listen(8888, address='127.0.0.1')
+        tornado.ioloop.IOLoop.instance().start()