How to change default language Chromium/Firefox using Playwright? - selenium-chromedriver

Question

I’ve been trying without success to change default language of browsers Chromium and Firefox (inside automated tests that run in parallel using CodeceptJS + Playwright as runner) to french language. In Chromium, I’ve tried to use args --lang without success and I’ve also tried to use prefs: intl.accept_languages. In Firefox, I’ve tried to use firefoxUserPrefs. Untill now, nothing has worked.
Does anybody know how to change default language in browser launched using playwright?
CodeceptJS version 3.0.6
Playwright version 1.10.0
Chrome version 90.0.4430.0
Firefox version 87.0b10
codecept.conf.js - full printscreen
codecept.conf.js
Playwright: {
url: process.env.baseUrl || DEFAULT_HOST,
show: true,
browser: 'chromium',
waitForAction: 250,
waitForNavigation: 'networkidle0',
chromium: {
channel: process.env.BROWSER,
args: ['--lang=fr-CA'],
prefs: {
'intl.accept_languages': 'fr-CA',
},
firefoxUserPrefs: {
'intl.accept_languages': 'fr-CA, fr',
},
},
},

Answer 1

browser.NewContext has an option called locale. You can use that option to change the language.

Answer 2

This might not have been available by the time of this question, but now there are emulation options for locale (and timezone) in Playwright (documentation here).
Can be specified both globally in config, per project, like this (in playwright.config.ts):
...
projects: [
{
name: 'chromium',
use: {
...devices['Desktop Chrome'],
locale: 'fr-CA',
},
},
...
or per test, like this:
test.use({
locale: 'sv-SE',
});
test('Lang test 1', async ({ page }) => {
// Test code
});