Can't mock library

Describe your environment

• React-Native version: 0.57.5
• OS version: Mac OS 10.13.6 (17G65)
• react-native-languages version: 3.0.1

How to repeat issue and example

After mocking

jest.mock('react-native-languages', () => ({
  RNLanguages: {
    language: 'en',
    languages: ['en'],
  },
}))

I had this error:

TypeError: Cannot set property 'locale' of undefined

      5 | I18n.locale = language

#I18n.ts
import { language } from 'react-native-languages'
import I18n from 'i18n-js'
import {ru, pl, uk, en} from './locales'

I18n.locale = language
....
export default I18n

[zoontek]

You can mock it like this:

jest.mock('react-native-localize', () => ({
  getLocales: () => [
    { countryCode: "GB", languageTag: "en-GB", languageCode: "en", isRTL: false },
    { countryCode: "US", languageTag: "en-US", languageCode: "en", isRTL: false },
    { countryCode: "FR", languageTag: "fr-FR", languageCode: "fr", isRTL: false },
  ],

  getNumberFormatSettings: () => ({
    decimalSeparator: ".",
    groupingSeparator: ",",
  }),

  getCalendar: () => "gregorian", // or "japanese", "buddhist"
  getCountry: () => "US", // the country code you want
  getCurrencies: () => ["USD", "EUR"], // can be empty array
  getTemperatureUnit: () => "celsius", // or "fahrenheit"
  getTimeZone: () => "Europe/Paris", // the timezone you want
  uses24HourClock: () => true,
  usesMetricSystem: () => true,

  addEventListener: jest.fn(),
  removeEventListener: jest.fn(),
}));

[zoontek]

@mikehardy I wrote an example in the README: https://github.com/react-native-community/react-native-localize/blob/master/README.md#how-to-test-your-code