This ViewHandler once installed will during development stage throw an IllegalStateException whenever an automatically generated JSF component ID (j_id...) is encountered in the rendered output. This has various advantages:
Keep the HTML output free of autogenerated JSF component IDs.
No need to fix the IDs again and again when the client side unit tester encounters an unusable autogenerated ID.
Make the developer aware which components are naming containers and/or implicitly require outputting its ID.
Note that this does not check every component for its ID directly, but instead checks the ResponseWriter for writes to the "id" attribute. Components that write their markup in any other way won't be checked and will thus slip through.
Register it as <view-handler> in faces-config.xml.