lens/docs/extensions/testing-and-publishing/testing.md

Testing extensions

Console.log

console.log() might be handy for extension developers to prints out info/errors from extensions. To use console.log, note that Lens is based on Electron. Electron has two types of processes: Main and Renderer.

Renderer process logs

console.log() in Renderer process is printed in the Console in Developer Tools (View > Toggle Developer Tools).

Main process logs

To view the logs from the main process is a bit trickier, since you cannot open developer tools for them. On MacOSX, one way is to run Lens from the terminal.

/Applications/Lens.app/Contents/MacOS/Lens

You can alos use Console.app to view logs from Lens.

On linux, you can get PID of Lens first

ps aux | grep Lens | grep -v grep

And get logs by the PID

tail -f /proc/[pid]/fd/1 # stdout (console.log)
tail -f /proc/[pid]/fd/2 # stdout (console.error)