How do I mock react-i18next and i18n.js in jest?

Question

package.json

"moduleNameMapper": {
  "i18next": "<rootDir>/__mocks__/i18nextMock.js"
}

i18n.js

import i18n from 'i18next'
import XHR from 'i18next-xhr-backend'
// import Cache from 'i18next-localstorage-cache'
import LanguageDetector from 'i18next-browser-languagedetector'

i18n
  .use(XHR)
  // .use(Cache)
  .use(LanguageDetector)
  .init({
    fallbackLng: 'en',
    // wait: true, // globally set to wait for loaded translations in translate hoc
    lowerCaseLng: true,
    load: 'languageOnly',
    // have a common namespace used around the full app
    ns: ['common'],
    defaultNS: 'common',
    debug: true,

    // cache: {
    //   enabled: true
    // },

    interpolation: {
      escapeValue: false, // not needed for react!!
      formatSeparator: ',',
      format: function (value, format, lng) {
        if (format === 'uppercase') return value.toUpperCase()
        return value
      }
    }
  })

export default i18n

i18nextMock.js

/* global jest */
const i18next = jest.genMockFromModule('react-i18next')
i18next.t = (i) => i
i18next.translate = (c) => (k) => k

module.exports = i18next

For some reason the jest unit tests are not getting a component.

Here is a unit test:

import React from 'react'
import { Provider } from 'react-redux'
import { MemoryRouter } from 'react-router-dom'
import { mount } from 'enzyme'

import { storeFake } from 'Base/core/storeFake'
import Container from '../container'

describe('MyContainer (Container) ', () => {
  let Component;

  beforeEach(() => {
    const store = storeFake({})

    const wrapper = mount(
      <MemoryRouter>
        <Provider store={store}>
          <Container />
        </Provider>
      </MemoryRouter>
    )

    Component = wrapper.find(Container)
  });

  it('should render', () => {
    // Component is undefined here
    expect(Component.length).toBeTruthy()
  })
})

Answer 1

You don't need to mock the t function, only the translate one is required. For the second one, your usage of the parameters are confusing, also, you need to return a Component.

I was able to make it work on my project. Here are my mock file and my Jest configuration

Jest configuration

"moduleNameMapper": {
    "react-i18next": "<rootDir>/__mocks__/reacti18nextMock.js"
}

The source code to mock react-i18next

/* global jest */
import React from 'react'

const react_i18next = jest.genMockFromModule('react-i18next')

const translate = () => Component => props => <Component t={() => ''} {...props} />

react_i18next.translate = translate

module.exports = react_i18next

Answer 2

I used Atemu's anwser in my jest tests, but ended up with the following one line in the mock:

module.exports = {t: key => key};

Also modified jest config as well since I import 't' from 'i18next':

"moduleNameMapper": {
    "i18next": "<rootDir>/__mocks__/reacti18nextMock.js"
}