How can I test electron-builder auto-update flow?

I built an Electron app and I am now looking at how to distribute it. I went with electron-builder to handle packaging etc.

For a bit of context, as a web developer, I am used to continuously deploy web apps on a web server but I have a hard time figuring out how to distribute a packaged one in Electron.

In electron-builder docs there is a brief mention about testing auto-update:

"Note that in order to develop/test UI/UX of updating without packaging the application you need to have a file named dev-app-update.yml in the root of your project, which matches your publish setting from electron-builder config (but in YAML format)"

But, it's rather vague...

So I actually have two questions:

1. How do I actually test the auto-update flow?

Do I need to actually publish a new version to trigger an update locally? Seems pretty unclear, it would be like developing against the production server.

2. Is it possible to have a fallback for unsigned code?

I don't have yet any certificate for code signing. So the OS/app will block the auto-update. But, I'd still want to tell the user that an update is available so they can go and download the app manually. Can I do that? (going back to point 1, I'd like to be able to test this flow)