What kind of data source? Can you be more specific?<p>If you're talking about Web APIs, you usually want to connect to an endpoint that gives you information about the user or the API.<p>Some APIs offer an 'echo' endpoint just for testing, other APIs offer an endpoint that provides information about the user account.
Google. It's been that way since I stopped using Yahoo! and Ask. Because of the almost guaranteed uptime of Google, it's the most trusted source, plus it's quick and easy to type.