I have set up a directory called "demo" inside this directory. It has a file called index.html which registers a service worker called serviceworker.js. The file, serviceworker.js, is also inside the demo directory.
Browsing to .../demo/ and going to dev tools enables some details to be seen about the service worker. Click on Storage to see what urls the service worker has cached. Click on Application to see the service workers registered for the page, when it was updated and to be able to unregister it and see if it is stopped or running and to start it if it is stopped.