How to test a React Native component that imports a custom native module with Jest?

Question

Here is a simple component that I am trying to test using React Native 0.39 and Jest 18:

// index.ios.js

import React, { Component } from \'react\';
import { Ap         


        

Answer 1

Jest is a JavaScript testing tool, it won't run code that you have written in Objective C/Swift/Java in a native module. You can mock the functionality of a native module so that you can call it from JavaScript by the approach you linked to. eg.

jest.mock('NetInfo', () => {
  return {
    isConnected: {
      fetch: () => {
        return new Promise((accept, resolve) => {
          accept(true);
        })
      }
    }
  }
});

Answer 2

This failed for me, too (react-native 0.57.5, jest 23.6.0). I was able to find a solution, but it was totally different (and in my case, a more elegant fix) than here.

Check out the ticket I filed for more details.

Essentially, I had to have NativeModules fleshed out by a function passed as the second parameter to jest.mock() and put this is in a script run at the beginning of each test using Jest's setupFiles config option.

Answer 3

This way, you will mock it once (before jest starts)

jest.config.js

module.exports = {
  preset: 'react-native',
  setupFiles: ['./__mocks__/your-native-bridge.js']
};

__mocks__/your-native-bridge.js

import {NativeModules} from 'react-native';

NativeModules.YourNativeBridge = {
  property: jest.fn()
};

Don't forget to mock all possible functions, properties in YourNativeBridge

Answer 4

You can simply add a mock where your native module should be:

import {
  NativeModules,
} from 'react-native';
import React from 'react';
import renderer from 'react-test-renderer';

describe('TestProject', () => {
  beforeEach(() => {
    NativeModules.TestModule = { test: jest.fn() } 
  });
  ...
});

Answer 5

#__mocks__/react-native-modules

const ReactNative = require('react-native')

ReactNative.NativeModules = {
  Defaults: {
    RU: {
      publicKey: '',
      privateKey: '',
    },
  },
}

module.exports = ReactNative

and then

# in test file
jest.mock('react-native-modules')
import 'react-native-modules'