How to use spawnJest method in Jest

In order to one among the expected value, you can reverse the comparison and test it using toContain method like

expect(addFeedForm.state().feedfrequency).toEqual('');
addFeedForm.simulate('change');
expect([6, 12, 24]).toContain(addFeedForm.state().feedfrequency) 

After hours looking in it, I found that what I needed to change was the way I was requiring react-intl package. So, I changed that line:

const Intl = require.requireActual('react-intl');

to that:

const Intl = jest.genMockFromModule('react-intl');

So the final file looks like this:

import React from 'react';
const Intl = jest.genMockFromModule('react-intl'); // <-- This is the change

const intl = {
  formatMessage: ({defaultMessage}) => defaultMessage
};

Intl.injectIntl = (Node) => (props) => <Node {...props} intl={intl}/>;

module.exports = Intl;

Hope this helps!

This bug should now be fixed

If your still having this problem, upgrade Jest to the latest version.

It seems this issue is to do with jests use of babel as the code coverage provider. Which is why switching to v8 works around this issue.

If you don't want to use v8 (this is marked as experimental currently). Then you will need to install babel into your build:

npm install --save-dev babel-jest @babel/core @babel/preset-env

Source

which should make the above error go away.

Since you are testing your heicUtils module, you should mock the heic2any lib, otherwise, you will be testing the 3rd party library instead of your own code.

In the mock, you should define the functions/methods of heic2any that your heicUtils use and what they should return for each test case you intend to write.

Examples of how to mock modules can be found here: https://jestjs.io/docs/manual-mocks

Presets are just plain Javascript objects, so in many circumstances you may simply merge them. For example, that's how I'm enabling ts-jest and jest-puppeteer simultaneously:

const merge = require('merge')
const ts_preset = require('ts-jest/jest-preset')
const puppeteer_preset = require('jest-puppeteer/jest-preset')

module.exports = merge.recursive(ts_preset, puppeteer_preset, {
    globals: {
        test_url: `http://${process.env.HOST || '127.0.0.1'}:${process.env.PORT || 3000}`,
    },
})

If there are certain options that can't be 'merged' like that, just handle these cases manually.

In Jest you have to pass a function into expect(function).toThrow(<blank or type of error>).

Example:

test("Test description", () => {
  const t = () => {
    throw new TypeError();
  };
  expect(t).toThrow(TypeError);
});

Or if you also want to check for error message:

test("Test description", () => {
  const t = () => {
    throw new TypeError("UNKNOWN ERROR");
  };
  expect(t).toThrow(TypeError);
  expect(t).toThrow("UNKNOWN ERROR");
});

If you need to test an existing function whether it throws with a set of arguments, you have to wrap it inside an anonymous function in expect().

Example:

test("Test description", () => {
  expect(() => {http.get(yourUrl, yourCallbackFn)}).toThrow(TypeError);
});

While it should be bundled with jsdom, it isn't with jsdom 16. Therefore you can polyfill like so:

import { TextEncoder, TextDecoder } from 'util'
global.TextEncoder = TextEncoder
global.TextDecoder = TextDecoder

Give a try:

If you have both react-scripts and jest in your package.json, delete jest from it. Then delete package-lock.json, yarn.lock and node_modules. Then run npm install (or yarn if you use it).

So if you're using yarn, run yarn install instead of npm install and try again.

From: https://github.com/facebook/jest/issues/5119

It should work. Here is a minimal working example:

./src/index.js:

export function sum(a, b) {
  return a + b;
}

./src/__tests__/index.spec.js:

import { sum } from "../";

it("should sum", () => {
  // eslint-disable-next-line
  console.log("localPath: ", localPath);
  const actualValue = sum(1, 2);
  expect(actualValue).toBe(3);
});

jest.config.js:

module.exports = {
  preset: "ts-jest/presets/js-with-ts",
  testEnvironment: "node",
  coverageReporters: ["json", "text", "lcov", "clover"],
  testMatch: ["**/__tests__/**/*.[jt]s?(x)", "**/?(*.)+(spec|test).[jt]s?(x)"],
  globals: {
    localPath: "Users/alex/Git/mytodolist"
  }
};

Unit test result:

 PASS  src/__tests__/index.spec.js
  ✓ should sum (4ms)

  console.log src/__tests__/index.spec.js:5
    localPath:  Users/alex/Git/mytodolist

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        2.233s
Ran all test suites.

As you can see, the value of global variable localPath has been set. Please print the global object and check in your tests.

Codesandbox: https://codesandbox.io/s/unruffled-feistel-byfcc