"Failed to execute 'requestFullscreen' on 'Element': API can only be initiated by a user gesture." toggle() called through global event or wrapper component about vue-fullscreen

[mirari]

requestFullscreen

This method must be invoked from a user interaction or a device orientation change, else it will fail.

Because of the browser security function, you can only call these methods by a user gesture, event bus can not work, just like the prop watch.
The second try should work, if you call the this.$test.startTest in a click callback.