react-native-background-timer: Jest: Invariant Violation: `new NativeEventEmitter()` requires a non-null argument.

The following error will be reported if jest is not configured

 FAIL  __tests__/App-test.tsx
  ● Test suite failed to run

    Invariant Violation: `new NativeEventEmitter()` requires a non-null argument.

       6 | import {IconButton, TouchableRipple} from 'react-native-paper';
       7 | import Ionicons from 'react-native-vector-icons/Ionicons';
    >  8 | import BackgroundTimer from 'react-native-background-timer';
         | ^
       9 | import dayjs from 'dayjs';
      10 | import relativeTime from 'dayjs/plugin/relativeTime';
      11 | import 'dayjs/locale/zh-cn';

      at invariant (node_modules/invariant/invariant.js:40:15)
      at new NativeEventEmitter (node_modules/react-native/Libraries/EventEmitter/NativeEventEmitter.js:44:7)
      at Object.<anonymous> (node_modules/react-native-background-timer/index.js:10:17)
      at Object.<anonymous> (src/screens/Home.tsx:8:1)
      at Object.<anonymous> (App.tsx:6:1)
      at Object.<anonymous> (__tests__/App-test.tsx:7:1)

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        4.29 s, estimated 7 s
Ran all test suites.
error Command failed with exit code 1.

So maybe we should configure jest manually, like:

// jest.setup.js
jest.doMock('react-native-background-timer', () => {
  return {
    stopBackgroundTimer: jest.fn(),
    runBackgroundTimer: jest.fn(),
  };
});

This allows the unit tests to pass with flying colors

repo here: https://github.com/shensven/ReadHubn/tree/5806faf354fbd178827aff9985efe4dea906c24d

test here: https://github.com/shensven/ReadHubn/runs/3824410010?check_suite_focus=true

About this issue

Original URL
State: open
Created 3 years ago
Comments: 18

Most upvoted comments

The suggested solution didn’t work for me.

While this error appears to come from react-native-background-timer, the true culprit, if you look carefully, is react-native/Libraries/EventEmitter/NativeEventEmitter, I solved this by adding the following to my jest.setup.js :

jest.mock('react-native/Libraries/EventEmitter/NativeEventEmitter');

+144

princefishthrower on Oct 28, 2021

i seem to be getting another error after doing this? i’m currently trying to mock deviceInfo module like so:

jest.mock('react-native-device-info', () => ({
  ...jest.requireActual('react-native-device-info'),
  getBuildNumber: jest.fn(() => 99),
}));

i got this error : Invariant Violation: new NativeEventEmitter() requires a non-null argument.

After adding the jest mock for NativeEventEmitter i get this error:

 react-native-device-info: NativeModule.RNDeviceInfo is null. To fix this issue try these steps:
      • For react-native <= 0.59: Run `react-native link react-native-device-info` in the project root.
      • Rebuild and re-run the app.
      • If you are using CocoaPods on iOS, run `pod install` in the `ios` directory and then rebuild and re-run the app. You may also need to re-open Xcode to get the new pods.
      If none of these fix the issue, please open an issue on the Github repository: https://github.com/react-native-device-info/react-native-device-info

ghost on Jun 21, 2022

jest.mock('react-native/Libraries/EventEmitter/NativeEventEmitter'); seems to work for me if I put it in the single test file, but not in jest.setup.json (I checked that the file is correctly loaded, and tried both with and without import { jest } from ‘@jest/globals’; I am curious as to why one works and not the other.

smarchesini-DQ on Jun 30, 2023

@AdamuAbba if you have Jest installed in your project you will find this file in the root of your project. The name of the file is jest.setup.js. If you are using VsCode, you can press Ctrl+P / Command+P and search by file name. Open that file and inside just paste the line mentioned by @princefishthrower

NanyThery on Oct 20, 2022

these two lines in ‘jest.setup.js’ fixed the issue for the same error in react-native-device-info

import mockRNDeviceInfo from "react-native-device-info/jest/react-native-device-info-mock"
jest.mock("react-native-device-info", () => mockRNDeviceInfo)

maybe it’s a similar issue

davidecarpini on Jul 13, 2023

The suggested solution didn’t work for me.

While this error appears to come from react-native-background-timer, the true culprit, if you look carefully, is react-native/Libraries/EventEmitter/NativeEventEmitter, I solved this by adding the following to my jest.setup.js :
jest.mock('react-native/Libraries/EventEmitter/NativeEventEmitter');

please where do I find this setup file? as all the answers seem vague

AdamuAbba on Oct 8, 2022