Is there a way to change the browser locale in Cypress?

Question

I have looked around online and quite a bit on stackoverflow and cant seem to find an up-to-date answer for this question. I have found other questions here, here, and here - and none of those solution work anymore. Does anyone know if this functionality is available in Cypress or if there's a way to force a locale change? Thanks

Answer 1

That's not too easy - as this differs from the browser you will be running your tests in.

Also, I believe that only are testing that your application looks and behaves right when the USER selected a specific language, you should consider adding a parameter when initiating your test session, e.g.

http://myapp.com/start?lang=en

then storing the selected language in LocaleStorage or a Cookie and selecting the language from there, as it is a lot more portable - and you will have users wanting to use your application in a different language than the browser default.

Still, There might be a few scenarios (e.g. if you want to tests, that your application detects the browser language correctly) where setting the browser language can be required, but I would suggest keeping tests that rely on a browser configuration to a minimum.

Is is possible tho, at least for Electron (verified with Electron 100) and Firefox (verified with Firefox 102). It used to work in Chrome too, but doesn't work for me anymore.

For Electron:

As Electron is being started along with the cypress GUI, changing the language afterwards is not possible. But you can expose an environment variable to the process, e.g.

ELECTRON_EXTRA_LAUNCH_ARGS=--lang=en npx cypress open

to start electron with the wanted locale.

For Firefox:

In your cypress.config.ts expand the defineConfig to contain such a block:

export default defineConfig({
  // ...
  e2e: {
    // ....
    setupNodeEvents(on, config) {
      on('before:browser:launch', (browser, launchOptions) => {

        if (browser.family === 'firefox') {
          launchOptions.preferences['intl.locale.requested'] = "en_US"
          return launchOptions
        }
      }
    }
  }

The Firefox Setup will only work, if you have no other Firefox instance running in another locale.