Testing Internationalisation and Locales

Internationalised applications must handle different languages, locales and formatting rules. Playwright can help you verify that translations appear correctly and that locale-specific formatting behaves as expected.

Testing Localised UI and Formatting #

You can pass locale or language settings via URLs, cookies, headers or configuration and then assert on translated text and formatting.

// i18n-locales.spec.ts
import { test, expect } from '@playwright/test';

test('shows translated text for German locale', async ({ page }) => {
  await page.goto('https://demo.myshop.com/de-DE');

  await expect(page.getByText('Warenkorb')).toBeVisible();
});

Internationalisation tests are particularly important for pricing, dates, number formatting and legal content, where mistakes may have serious consequences.

Common Mistakes #

Mistake 1 — Using English-only selectors for localised tests #

This is brittle.

❌ Wrong: Selecting elements by English text when you expect translations.

✅ Correct: Use roles, test IDs or language-agnostic attributes.

Mistake 2 — Testing only one locale #

This misses regional differences.

❌ Wrong: Assuming that if it works in en-US, it works everywhere.

✅ Correct: Identify key locales based on user base and test those explicitly.