Mine

<VirtualHost *>
        ...standard virtual host stuff above here
        ProxyRequests Off
        <Proxy *>
                Order deny,allow
                Allow from all
        </Proxy>

        # This ensures that the results from the proxying rewrite rules
        # get sent out correctly
        ProxyPassReverse / http://127.0.0.1:8080/app-testing/

        ProxyErrorOverride On
        ErrorDocument 404 "This is a test error"

        RewriteEngine On
        ...rewrite rules all down here
</VirtualHost>