jest test fails after installing react-native-async-storage

Question

In my react native project, I have recently installed node module react-native-async-storage as I received warnings about the native package from 'react-native' being deprecated and moved out to an individual module.

After installing the @react-native-community/async-storage my jest test is failing.

first with following error: unexpected token at position 0

in file:

persistence.js

import AsyncStorage from '@react-native-community/async-storage';

storeData = async ({ key, value }) => {
  try {
    await AsyncStorage.setItem(key, value);
  } catch (error) {
    // Error saving data
  }
}

retrieveData = async (key) => {
  try {
    const value = await AsyncStorage.getItem(key);
    if (value !== null) {
      // Our data is fetched successfully
      return value;
    }
  } catch (error) {
    // Error retrieving data
  }
}

module.exports = {
  storeData,
  retrieveData
}

So I assume this is related to some babel configuration, since i encountered something similar last time i installed a package from the @react-native-community

So, to the transformIgnorePatterns in my package.json I added following:

  "jest": {
    "preset": "react-native",
    "transformIgnorePatterns": [
      "node_modules/(?!react-native|@react-native-community/async-storage|native-base-shoutem-theme|@shoutem/animation|@shoutem/ui|tcomb-form-native)"
    ]
  }

But now I'm getting a new error. @RNCommunity/AsyncStorage: NativeModule.RCTAsyncStorage is null.

I'm pasting the screenshot to show my project dir so that you can get an idea about which config files a have available to mess with.

As I can see most related topic are about mocking the asyncStorage function I've tried to do so, without any luck. I added following to my one and only tests file:

import MockAsyncStorage from 'mock-async-storage';

beforeAll(() => { 
  const mockImpl = new MockAsyncStorage()
  jest.mock('AsyncStorage', () => mockImpl)
  snapshot = renderer.create(<App />);
})

afterAll(() => {
  jest.unmock('AsyncStorage')
});

Still no cigar. I have tried adding a setupFilesAfterEnv.js with configurations as other answer suggests, also didn't do the trick.

Answer 1

async-storage has published instructions on how to solve this issue.

Here is a shorten version:

1. In your project root directory, create __mocks__/@react-native-community directory.
2. Inside that folder, create a async-storage.js file.
3. Copy paste the following inside that file:

export default from '@react-native-community/async-storage/jest/async-storage-mock'

4. Enjoy!

I hope it can help others.

Answer 2

You can add this to your test file.

jest.mock("@react-native-community/async-storage", () =>
  require("@react-native-community/async-storage/jest/async-storage-mock"),
);

For example

import React from "react";

jest.mock("@react-native-community/async-storage", () =>
  require("@react-native-community/async-storage/jest/async-storage-mock"),
);

describe("Example test", () => {
  it("should work", () => {
    ...
  });
});

Answer 3

I found a way of mocking the @react-native-community/async-storage

in root of my project, (same dir as __test__ dir), I created a dir structure like this:

__mocks__/@react-native-community/async-storage/index.js

in index.js I mocked the following functions:

let cache = {};
export default {
  setItem: (key, value) => {
    return new Promise((resolve, reject) => {
      return (typeof key !== 'string' || typeof value !== 'string')
        ? reject(new Error('key and value must be string'))
        : resolve(cache[key] = value);
    });
  },
  getItem: (key, value) => {
    return new Promise((resolve) => {
      return cache.hasOwnProperty(key)
        ? resolve(cache[key])
        : resolve(null);
    });
  },
  removeItem: (key) => {
    return new Promise((resolve, reject) => {
      return cache.hasOwnProperty(key)
        ? resolve(delete cache[key])
        : reject('No such key!');
    });
  },
  clear: (key) => {
    return new Promise((resolve, reject) => resolve(cache = {}));
  },

  getAllKeys: (key) => {
    return new Promise((resolve, reject) => resolve(Object.keys(cache)));
  },
}

in my test file i added this:

beforeAll(() => { 
  jest.mock('@react-native-community/async-storage');
})

Screenshot of dir structure:

This did the trick. I found inspiration here: https://github.com/react-native-community/react-native-async-storage/issues/39

Answer 4

You need to add this piece of code to your setupTestFrameworkScriptFile

    import { NativeModules } from 'react-native';
NativeModules.RNCAsyncStorage = {
  getItem: jest.fn(),
  setItem: jest.fn(),
  removeItem: jest.fn(),
  mergeItem: jest.fn(),
  clear: jest.fn(),
  getAllKeys: jest.fn(),
  flushGetRequests: jest.fn(),
  multiGet: jest.fn(),
  multiSet: jest.fn(),
  multiRemove: jest.fn(),
  multiMerge: jest.fn(),
};