This works by calling a SOAP service listed on X Methods Website. View the source of this page for details on how it was called. If you compile mozilla DEBUG (you also need MOZ_SOAP), the message sent and received will be logged to the console. Notice that the response seems to be using an incorrect namespaceURI to identify the type of the returned boolean. For this reason, the script receives the value as a string instead of as a boolean, which is why it is necessary to compare it as a string.
Experimenters may wish to add other tests which exercize services, with specific user interfaces such as the one in this test.