Seeking web page or small install GIS client to test WMS URL

Try to check your WMS with the firefox plug-in - "WMS Inspector" - see github page https://github.com/amercader/WMS-Inspector/wiki

A quick and easy way to do this would be using jsfiddle. You can just load the javascript mapping library of your choice and do a let more than just test the WMS URL.

This is using Leaflet. Just replace the WMS url with your own and click 'Run' http://jsfiddle.net/tmoy0f0g/1/