Rename websocket.js to websocket.sub.js. This makes it impossible to forget the substitution. 
diff --git a/websockets/Close-reason-unpaired-surrogates.htm b/websockets/Close-reason-unpaired-surrogates.htm index cabbe97..9ad8d61 100644 --- a/websockets/Close-reason-unpaired-surrogates.htm +++ b/websockets/Close-reason-unpaired-surrogates.htm 
@@ -4,7 +4,7 @@  <title>W3C WebSocket API - Close WebSocket - Reason with unpaired surrogates</title>  <script type="text/javascript" src="/resources/testharness.js"></script>  <script type="text/javascript" src="/resources/testharnessreport.js"></script> - <script type="text/javascript" src="websocket.js?pipe=sub"></script> + <script type="text/javascript" src="websocket.sub.js"></script>  </head>  <body>  <div id="log"></div>