My question is somehow similar to this other thread, but in my case I want to test a WFS service:
I look for an online service which lets me add the url of a WFS gazetter service, and then exposes the layers and features available and lets me make filtered requests to that gazetter (i.e. look for a place name) using a web interface.
In other words: I am tired of trying to construct the right requests on my own. I am not being able to adapt requests from documentation and examples (there are many differences between WFS versions, namespaces, and so on ...)