Cannot find module from 'react-native-implementation.js'

Question

I have the following Jest test:

import React from 'react';
import IndexSign from '../IndexSign';
import renderer from 'react-test-renderer';

it('renders correctly', () => {
  const tree = renderer.create(
    <IndexSign index={1}/>
  ).toJSON();
  expect(tree).toMatchSnapshot();
});

The IndexSign component that I am calling calls this StyleSheet component:

import {StyleSheet} from 'react-native';

export default StyleSheet.create({
  //some styles
});

For testing, I am using Gulp:

gulp.task('tests', () => {
    process.env.NODE_ENV = 'test';
    return gulp.src('src').pipe(jest({
    }));
});

The problem is that when I run this test, I get:

● Test suite failed to run

Cannot find module 'StyleSheet' from 'react-native-implementation.js'

  at Resolver.resolveModule (../node_modules/jest-resolve/build/index.js:142:17)
  at Object.StyleSheet (../node_modules/react-native/Libraries/react-native/react-native-implementation.js:98:25)
  at Object.<anonymous> (styles/Styles.js:5:13)

Any idea why this is happening?

Why is it searching for StyleSheet in react-native-implementation.js rather than react-native, which I imported?

And why can it not find StyleSheet?

Answer 1

I ran into the same issue. Adding

"jest": {
    "preset": "react-native"
},

in the package.json fixed the error for me.

Incase you are keeping separate config file like jest.config.js. Add preset in it. Checkout the sample config file

module.exports = {
  preset: 'react-native',
  setupFiles: ['<rootDir>/__test__/setup.js'],
  moduleNameMapper: {
    '\\.(css|less)$': 'identity-obj-proxy',
    '^.+\\.(jpg|jpeg|gif|png|mp4|mkv|avi|webm|swf|wav|mid)$': 'jest-static-stubs/$1'
  },
  globals: {
    __DEV__: true
  },
  collectCoverageFrom: [
    '**/src/**/*.{js,jsx}',
    '!**/src/**/style.js',
    '!**/src/**/index.js',
    '!**/src/theme/**',
    '!**/android/**',
    '!**/ios/**',
    '!**/node_modules/**',
    '!**/scripts/**',
    '!**/__test__/**'
  ],
  verbose: true,
  testPathIgnorePatterns: ['/node_modules/'],
  testResultsProcessor: 'jest-sonar-reporter',
  testURL: 'http://localhost/'
}

Answer 2

There are two ways of fixing this issue.
1. Make sure you don't have or delete any file called jest.config.js in your root folder.
2. If you want to have a custom jest.config.js file, make sure you have a preset node in it.
Like so：

 module.exports = {
    preset: "react-native",
    verbose: true,
  };