Use the "builders" version of the driver configuration:
"driver": {
"builders": {
"forBrowser": ["firefox"],
"setFirefoxOptions": ["require:./firefoxProfile"]
}
},
The "firefoxProfile.js" file:
'use strict';
const firefox = require('selenium-webdriver/firefox');
let profile = new firefox.Profile();
//set any profile options here
profile.setPreference('extensions.firebug.showChromeErrors', true);
profile.addExtension('/path/to/firebug.xpi');
let options = new firefox.Options().setProfile(profile);
module.exports = options;
That's it!