React NativeのAppStateのモックのスニペット

AppState.mock.example.ts

import { renderHook, act } from '@testing-library/react-hooks'
import { AppState, AppStateStatus } from 'react-native'

let appStateAddEventListenerHandlerMock: (
  nextAppStateStatus: AppStateStatus,
) => void

// NOTE: fetchをモックしておくためにglobalに型を生やす
type FetchMock = NodeJS.Global & {
  fetch: unknown
}

beforeEach(() => {
  jest.clearAllMocks()

  // fetchをモックしておく
  ;(global as FetchMock).fetch = jest.fn()
  // AppStateをモックしておく
  jest.mock('react-native/Libraries/AppState/AppState', () => ({
    addEventListener: jest.fn(
      (_event: string, fn: (nextAppStateStatus: AppStateStatus) => unknown) => {
        // NOTE: テスト上、任意のタイミングでイベントタイプを添えてハンドラを発火できるようにモックを変数に格納しておく
        appStateAddEventListenerHandlerMock = (
          nextAppStateStatus: AppStateStatus,
        ) => {
          fn(nextAppStateStatus)
        }
      },
    ),
    removeEventListener: jest.fn(
      (_event: string, fn: (nextAppStateStatus: AppStateStatus) => unknown) => {
        return (nextAppStateStatus: AppStateStatus) => {
          fn(nextAppStateStatus)
        }
      },
    ),
  }))
})