You can also have a look at the literature on the subject (Splaine, Nguyen and Whittaker come to mind as good authors on the subject).
You can look at the white papers from some tools vendors, and try using some demonstration (or trial) version of such tools. I would suggest eValid (www.soft.com/evalid) as it covers different aspects of web site analysis such as functional, performance and web-spider (to analyse all URLs and provide size and loading info about them).
Your question is vague, not sure what exactly you want to test, anyway if you want to test the API's through web services then there a tool called SoapScope where in the tool provides the input filed for the APIs once you show the WSDL file of your web service. For more info. goto the www.mindreef.com and download the tool and see if it can help you.
I don't think my question is vague, I have just requested for some documentation as i am new to web services concepts. I am not here to start Testing something which i donot know.
Anyway thanks for your Inputs which helped me [img]images/icons/smile.gif[/img]