Say that you detect an error by sending a spezific request to a webservice you use. You did record that request with for example firefox liveheader plugin.
The error report could easily be done with the following script
Error Report Script
_REQ webservice 80
__GET /my/service?parm=value HTTP/1.1
_EXPECT . "200 OK"
_EXPECT . "foo"
The script will fail cause there is no "200 OK" but for example a "500 Server Error" or the result "foo" do not apeare in the page.