Testing

In case you want to make tests with next-international, you will need to create a custom render. The following example uses @testing-library and Vitest, but should work with Jest too.

// customRender.tsx
import { ReactElement } from 'react'
import { cleanup, render } from '@testing-library/react'
import { afterEach } from 'vitest'
 
afterEach(() => {
  cleanup()
})
 
const customRender = (ui: ReactElement, options = {}) =>
  render(ui, {
    // wrap provider(s) here if needed
    wrapper: ({ children }) => children,
    ...options,
  })
 
export * from '@testing-library/react'
export { default as userEvent } from '@testing-library/user-event'
export { customRender as render }

You will also need your locales files, or one for testing purposes.

// en.ts
export default {
  hello: 'Hello',
} as const

Then, you can later use it in your tests:

// *.test.tsx
import { describe, vi } from 'vitest'
import { createI18n } from 'next-international'
import { render, screen, waitFor } from './customRender' // Our custom render function.
import en from './en' // Your locales.
 
// Don't forget to mock the "next/router", not doing this may lead to some console errors.
beforeEach(() => {
  vi.mock('next/router', () => ({
    useRouter: vi.fn().mockImplementation(() => ({
      locale: 'en',
      defaultLocale: 'en',
      locales: ['en', 'fr'],
    })),
  }))
})
 
afterEach(() => {
  vi.clearAllMocks()
})
 
describe('Example test', () => {
  it('just an example', async () => {
    const { useI18n, I18nProvider } = createI18n({
      en: () => import('./en'),
    })
 
    function App() {
      const t = useI18n()
 
      return <p>{t('hello')}</p>
    }
 
    render(
      <I18nProvider locale={en}>
        <App />
      </I18nProvider>
    )
 
    expect(screen.queryByText('Hello')).not.toBeInTheDocument()
 
    await waitFor(() => {
      expect(screen.getByText('Hello')).toBeInTheDocument()
    })
  })
})

Writing locales Examples