Ask HN: After connecting to a data source, what URL do you visit to test?

What kind of data source? Can you be more specific?

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.

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.