.NET Webservice Studio is a tool to invoke webmethods interactively. The user can provide a WSDL endpoint. On clicking button Get the tool fetches the WSDL, generates .NET proxy from the WSDL and displays the list of methods available. The user can choose any method and provide the required input parameters. On clicking Invoke the SOAP request is sent to the server and the response is parsed to display the return value.
[ GotDotNet User Sample: WebServiceStudio 2.0 ]
Sure you can do some testing with the interactive pages that ASP.NET creates for you, but in my case authentication was done via extra SOAP headers, which cannot be tested in the auto generated webpages. In addition some of the methods took complex objects as attributes, which also cannot be tested in the auto generated webpages.
This tool will get the WSDL and write the same wrappers that you would get in a .NET program, then (through reflection) allow you to specify the parameters passed in and interactively call each method. Without this tool the Web Service that I worked on today would have take 2-5 times as long, since I always do in depth testing of my work. 