The goal of this assignment is to begin the process of integrating Jest tests into WebCrafts.

From the root of your WebCraft project:

npm install --save-dev jest enzyme-adapter-react-16
npm install --save-dev react-test-renderer enzyme
npm install --save-dev babel-preset-stage-0
mkdir source/__tests__
ln -s node_modules/.bin/jest .

Set up Babel

In the root of your project create a .babelrc file:

  "presets": ["env", "stage-0", "react"]

The Jest Install

when we ran npm install jest, Jest was installed here:


The NPM install also placed a script to run Jest here:


In a previous part of this assignment, we created a link to the Jest script like this:

ln -s node_modules/.bin/jest .

This means you can run Jest from the root of your project with either of these commands:


Alternatively, you can set up your tests in package.json as described below in the section called NPM.


In package.json rename the old scripts/test property to karma-test and set up a new test script:

"scripts": {
    "test": "jest",
    "karma-test": "karma start",
    "start": "nodemon ./bin/www",
    "bundle": "node_modules/.bin/webpack"


To run jest, you can just do one of the following:

./jest --watch
./jest --coverage
./jest --watch --coverage

If you choose the watch option your tests should be automatically rerun when you update your code.

If you use the coverage option you should be able to see if your tests are run against all of the code in your program. We will talk about code coverage more in class, or you can research this subject on the web.

When using Jest 21.2.1, I can see code coverage at the command line and create a coverage directory by passing –coverage to the jest script. Below are some examples.

I tend to install Jest locally, in which case the command might look like this:

node_modules/.bin/jest --coverage

I assume, but have not confirmed, that this would also work if I installed Jest globally:

jest --coverage

The very sparse docs are here:

When I navigated into the coverage/lcov-report directory I found an index.html file that could be loaded into a browser. It included the information printed at the command line, plus additional information and some graphical output.


Find it here.

Or choose the Raw view of the code on GitHub, and then:

cd source


Here are a few simple tests that you can save into a file called sanity.js. Study them carefully. Also add a test that shows that HomeButtons can render without crashing.

import React from 'react';
import ReactDOM from 'react-dom';
import ReactHome from '../ReactHome';
import HomeButtons from '../HomeButtons';
import {configure, shallow} from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
import ElfDebugEnzyme from '../ElfDebugEnzyme';
const elfDebugEnzyme = new ElfDebugEnzyme(true, 'sanity');
configure({adapter: new Adapter()});
import jQuery from 'jquery';
global.jQuery = jQuery;
global.$ = jQuery;
import '../fake-pub-sub';
import raf from '../temp-poly-fills';

describe('WebCrafts Sanity Test', function() {

    'use strict';

    it('expects true to be true', function() {

    it('renders without crashing', () => {
        const div = document.createElement('div');
        ReactDOM.render(<ReactHome/>, div);

    it('renders default value of H1 tag', () => {
        const wrapper = shallow(<ReactHome/>);
        const h1tag = <h1>An H1 element in a React Component</h1>;
        elfDebugEnzyme.getLast(wrapper, 'h1', true);


Get the latest packages:

npm install -g npm-check-updates
ncu -a
npm update

Turn it in

I’m looking for evidence that you have integrated Jest into your project, and added a few tests for some of your components. I’m not looking for complete testing, just evidence that you have started the process.


  • Jest in package.json with a test command
  • A .babelrc file.
  • Passing tests that reference at least two of your components.
    • I’ll run: npm install && npm test