Testing

📄 Mirrors docs/testing.md in the main repo — the repo version is canonical.

Testing

Status: planned / pre-release. This page documents the intended API of next-tongue. Nothing is published yet; names may change before v1.0. See ROADMAP.

Unit tests (Vitest/Jest)

import { createTestT } from 'next-tongue/testing';

const t = createTestT('de', 'home');
expect(t('inbox', { count: 2 })).toBe('2 Nachrichten');

createTestT uses the same compiled modules as the app (run tongue build first, e.g. in a Vitest globalSetup; no Vite plugin needed).

Component tests (Testing Library)

import { render, screen } from '@testing-library/react';
import { TongueTestProvider } from 'next-tongue/testing';

render(<TongueTestProvider locale="de"><InboxBadge count={1} /></TongueTestProvider>);
expect(screen.getByText('1 Nachricht')).toBeInTheDocument();

Pass keysOnly to render keys instead of text (home.inbox) for locale-independent snapshot tests.

Async server components

Test the logic by calling the component function and rendering the result, or prefer e2e for RSC.

E2E (Playwright)

Test each locale's URL directly (/de/about) and test the proxy separately with Accept-Language headers:

test('redirects German browsers', async ({ browser }) => {
  const ctx = await browser.newContext({ locale: 'de-DE' });
  const page = await ctx.newPage();
  await page.goto('/about');
  await expect(page).toHaveURL(/\/de\/ueber-uns$/);
});

CI

Run tongue check before tests; it is faster than a build and catches most i18n regressions.