> For the complete documentation index, see [llms.txt](https://react.i18next.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://react.i18next.com/misc/testing.md).

# Testing

Testing components that use react-i18next: export the plain component or test without stubbing, with an example i18next configuration for tests.

For testing purpose of your component you should export the pure component without extending with the withTranslation hoc and test that:

```javascript
export MyComponent;
export default withTranslation('ns')(MyComponent);
```

In the test, test the myComponent export passing a t function mock:

```javascript
import { MyComponent } from './myComponent';

<MyComponent t={key => key} />
```

Or create a manual mock in `__mocks__/react-i18next.js` (picked up automatically by jest) that covers `useTranslation`, `withTranslation` and `<Trans>` in one place, so components mixing all three render their keys and children as plain text:

```jsx
const React = require('react');
const reactI18next = require('react-i18next');

const useMock = [(k) => k, { changeLanguage: () => new Promise(() => {}) }];
useMock.t = (k) => k;
useMock.i18n = { changeLanguage: () => new Promise(() => {}) };

module.exports = {
  ...reactI18next,
  withTranslation: () => (Component) => (props) => <Component t={(k) => k} {...props} />,
  Trans: ({ children, i18nKey }) => children ?? i18nKey,
  useTranslation: () => useMock,
};
```

A more complete version of this mock (including a `<Trans>` mock that renders nested elements) is part of the runnable jest example: [example/test-jest/src/\_\_mocks\_\_/react-i18next.js](https://github.com/i18next/react-i18next/blob/master/example/test-jest/src/__mocks__/react-i18next.js)

Or mock it like:

```javascript
jest.mock('react-i18next', () => ({
  // this mock makes sure any components using the translate HoC receive the t function as a prop
  withTranslation: () => Component => {
    Component.defaultProps = { ...Component.defaultProps, t: (i18nKey) => i18nKey };
    // or with TypeScript:
    //Component.defaultProps = { ...Component.defaultProps, t: (i18nKey: string) => i18nKey };
    return Component;
  },
}));
```

Or, when using the `useTranslation` hook instead of `withTranslation`, mock it like:

```javascript
jest.mock('react-i18next', () => ({
  // this mock makes sure any components using the translate hook can use it without a warning being shown
  useTranslation: () => {
    return {
      t: (i18nKey) => i18nKey,
      // or with TypeScript:
      //t: (i18nKey: string) => i18nKey,
      i18n: {
        changeLanguage: () => new Promise(() => {}),
      },
    };
  },
  initReactI18next: {
    type: '3rdParty',
    init: () => {},
  }
}));
```

or, you can also spy the `t` function:

{% tabs %}
{% tab title="JavaScript" %}

<pre class="language-jsx"><code class="lang-jsx"><strong>// implementation
</strong>import React from 'react';
import { useTranslation } from 'react-i18next';

export default function CustomComponent() {
  const { t } = useTranslation();

  return &#x3C;div>{t('some.key', { some: 'variable' })}&#x3C;/div>;
}

<strong>// test
</strong>import React from 'react';
import { render, screen } from '@testing-library/react';
import UseTranslationWithInterpolation from './UseTranslationWithInterpolation';
import { useTranslation } from 'react-i18next';

jest.mock('react-i18next', () => ({
  useTranslation: jest.fn(),
}));

it('test render', () => {
  const useTranslationSpy = useTranslation;
  const tSpy = jest.fn((str) => str);
  useTranslationSpy.mockReturnValue({
    t: tSpy,
    i18n: {
      changeLanguage: () => new Promise(() => {}),
    },
  });

  render(&#x3C;UseTranslationWithInterpolation />);

  expect(screen.getByText('some.key')).toBeInTheDocument();

  // If you want you can also check how the t function has been called,
  // but basically this is testing your mock and not the actual code.
  expect(tSpy).toHaveBeenCalledTimes(1);
  expect(tSpy).toHaveBeenLastCalledWith('some.key', { some: 'variable' });
});
</code></pre>

{% endtab %}

{% tab title="TypeScript" %}

<pre class="language-tsx"><code class="lang-tsx"><strong>// implementation
</strong>import React from 'react';
import { useTranslation } from 'react-i18next';

export default function CustomComponent() {
  const { t } = useTranslation();

  return &#x3C;div>{t($ => $.some.key, { some: 'variable' })}&#x3C;/div>;
}

<strong>// test
</strong>import React from 'react';
import { render, screen } from '@testing-library/react';
import UseTranslationWithInterpolation from './UseTranslationWithInterpolation';
import { useTranslation } from 'react-i18next';

jest.mock('react-i18next', () => ({
  useTranslation: jest.fn(),
}));

it('test render', () => {
  const useTranslationSpy = useTranslation;
  const tSpy = jest.fn((str) => str);
  useTranslationSpy.mockReturnValue({
    t: tSpy,
    i18n: {
      changeLanguage: () => new Promise(() => {}),
    },
  });

  render(&#x3C;UseTranslationWithInterpolation />);

  expect(screen.getByText('some.key')).toBeInTheDocument();

  // If you want you can also check how the t function has been called,
  // but basically this is testing your mock and not the actual code.
  expect(tSpy).toHaveBeenCalledTimes(1);
  expect(tSpy).toHaveBeenLastCalledWith('some.key', { some: 'variable' });
});
</code></pre>

{% endtab %}
{% endtabs %}

{% hint style="success" %}
You can find a full sample for testing with jest here: <https://github.com/i18next/react-i18next/tree/master/example/test-jest>
{% endhint %}

## Testing without stubbing

Alternatively, you could also test I18next without stubbing anything, by providing the correct configuration and fully wrapping your container in the provider.

### Example configuration for testing

```javascript
import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';

i18n
  .use(initReactI18next)
  .init({
    lng: 'en',
    fallbackLng: 'en',

    // have a common namespace used around the full app
    ns: ['translationsNS'],
    defaultNS: 'translationsNS',

    debug: true,

    interpolation: {
      escapeValue: false, // not needed for react!!
    },

    resources: { en: { translationsNS: {} } },
  });

export default i18n;
```

### Example test using this configuration

```javascript
import React from 'react';
import { Provider } from 'react-redux';
import { render, fireEvent } from '@testing-library/react';
import { I18nextProvider } from 'react-i18next';
import configureStore from 'redux-mock-store';
import ContactTable from './ContactTable';
import actionTypes from '../constants';
import i18n from '../i18nForTests';

const mockStore = configureStore([]);
const store = mockStore({ contacts: [ ] });

it('dispatches SORT_TABLE', () => {
  const { container } = render(
    <Provider store={store}>
      <I18nextProvider i18n={i18n}>
        <ContactTable />
      </I18nextProvider>
    </Provider>
  );
  fireEvent.click(container.querySelector('.sort'));
  const actions = store.getActions();
  expect(actions).toEqual([{ type: actionTypes.SORT_TABLE }]);
});
```

As translations aren't provided, `this.props.i18n.language` will be `undefined`. In case your application relies on that value you can mock resources by adding these lines to the object passed to init:

```
i18n
  .init({
    ...
    fallbackLng: 'en',
    resources: {
      en: {},
      de: {}
    }
  })
```

Now in your component `this.props.i18n.language` will return `en`.