Testing Web services is a tricky task because of the currently limited choice of tools. In an effort to fill the gap the Web Services Interoperability Organization (WS-I), an open industry effort set up to promote Web services interoperability across platforms, applications, and programming languages, has released a set of utilities to monitor and analyze Web service data exchanges.
The underlying principle of the tools is conformance with the WS-I Basic Profile, which aims to provide interoperability guidance for core Web services specifications such as Simple Object Application Protocol (SOAP), Web Services Description Language (WSDL), and Universal Description, Discovery, and Integration (UDDI).
The utilities, referred to as the Implementation Tools, consist of a Web Service Monitor and a Web Service Profile Analyzer. They are released as open source freeware and are available in Java and C#.
The Web Service Monitor uses the "Man in the Middle" architecture - essentially a relay server - which maps a request coming in on a particular port to a specific target machine. This compares to the more complex proxy server architecture where all requests are accepted on a single port and then resent to the target machines.
The Web Service Monitor logs all SOAP transaction data in an XML format. This means that all HTTP verbs that don't apply to SOAP are ignored. Also note that the current release of the Monitor doesn't handle Secure Sockets Layer.
The Web Service Profile Analyzer analyzes messages captured by the monitor and checks the WSDL definitions, XML schema files, and UDDI registration and produces a report on whether the interoperability requirements of the WS-I Basic Profile are met.
This is an interesting tool and has potential when you are working with third parties and trying to establish the grounds for interoperability (or the reasons for the lack thereof).