├── .gitignore
├── README.md
├── package.json
├── public
├── favicon.ico
├── index.html
├── logo192.png
├── logo512.png
├── manifest.json
└── robots.txt
├── src
├── App.css
├── App.js
├── App.test.js
├── __snapshots__
│ └── App.test.js.snap
├── components
│ ├── TestAsync.js
│ ├── TestAsync.test.js
│ ├── TestAxios.js
│ ├── TestAxios.test.js
│ ├── TestContext.js
│ ├── TestContext.test.js
│ ├── TestElements.js
│ ├── TestElements.test.js
│ ├── TestEvents.js
│ ├── TestEvents.test.js
│ ├── TestRedux.js
│ ├── TestRedux.test.js
│ ├── TestRouter.js
│ └── TestRouter.test.js
├── index.css
├── index.js
├── logo.svg
├── serviceWorker.js
├── setupTests.js
└── store
│ └── reducer.js
└── yarn.lock
/.gitignore:
--------------------------------------------------------------------------------
1 | # See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
2 |
3 | # dependencies
4 | /node_modules
5 | /.pnp
6 | .pnp.js
7 |
8 | # testing
9 | /coverage
10 |
11 | # production
12 | /build
13 |
14 | # misc
15 | .DS_Store
16 | .env.local
17 | .env.development.local
18 | .env.test.local
19 | .env.production.local
20 |
21 | npm-debug.log*
22 | yarn-debug.log*
23 | yarn-error.log*
24 |
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | # 8 simple steps to start testing React Apps using React Testing Library and Jest
2 |
3 | 1. How to create a test snapshot?
4 | 2. Testing DOM elements
5 | 3. Testing events
6 | 4. Testing asynchronous actions
7 | 5. Testing React Redux
8 | 6. Testing React Context
9 | 7. Testing React Router
10 | 8. Testing HTTP Request (axios)
11 |
12 | Find the full article on [my blog](https://www.ibrahima-ndaw.com/blog/react-testing-library-guide/)
13 |
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/package.json:
--------------------------------------------------------------------------------
1 | {
2 | "name": "react-testing-library-guide",
3 | "version": "0.1.0",
4 | "private": true,
5 | "dependencies": {
6 | "@testing-library/jest-dom": "^4.2.4",
7 | "@testing-library/react": "^9.3.2",
8 | "@testing-library/user-event": "^7.1.2",
9 | "axios": "^0.19.2",
10 | "react": "^16.13.0",
11 | "react-dom": "^16.13.0",
12 | "react-redux": "^7.2.0",
13 | "react-router-dom": "^5.1.2",
14 | "react-scripts": "3.4.0",
15 | "redux": "^4.0.5"
16 | },
17 | "scripts": {
18 | "start": "react-scripts start",
19 | "build": "react-scripts build",
20 | "test": "react-scripts test",
21 | "eject": "react-scripts eject"
22 | },
23 | "eslintConfig": {
24 | "extends": "react-app"
25 | },
26 | "browserslist": {
27 | "production": [
28 | ">0.2%",
29 | "not dead",
30 | "not op_mini all"
31 | ],
32 | "development": [
33 | "last 1 chrome version",
34 | "last 1 firefox version",
35 | "last 1 safari version"
36 | ]
37 | }
38 | }
39 |
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/public/favicon.ico:
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https://raw.githubusercontent.com/ibrahima92/react-testing-library-guide/076ad72b89caced302dfc09cde009cb97ed8ede9/public/favicon.ico
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/public/index.html:
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
12 |
13 |
17 |
18 |
27 | React App
28 |
29 |
30 |
31 |
32 |
42 |
43 |
44 |
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/public/logo192.png:
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https://raw.githubusercontent.com/ibrahima92/react-testing-library-guide/076ad72b89caced302dfc09cde009cb97ed8ede9/public/logo192.png
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/public/logo512.png:
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https://raw.githubusercontent.com/ibrahima92/react-testing-library-guide/076ad72b89caced302dfc09cde009cb97ed8ede9/public/logo512.png
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/public/manifest.json:
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1 | {
2 | "short_name": "React App",
3 | "name": "Create React App Sample",
4 | "icons": [
5 | {
6 | "src": "favicon.ico",
7 | "sizes": "64x64 32x32 24x24 16x16",
8 | "type": "image/x-icon"
9 | },
10 | {
11 | "src": "logo192.png",
12 | "type": "image/png",
13 | "sizes": "192x192"
14 | },
15 | {
16 | "src": "logo512.png",
17 | "type": "image/png",
18 | "sizes": "512x512"
19 | }
20 | ],
21 | "start_url": ".",
22 | "display": "standalone",
23 | "theme_color": "#000000",
24 | "background_color": "#ffffff"
25 | }
26 |
--------------------------------------------------------------------------------
/public/robots.txt:
--------------------------------------------------------------------------------
1 | # https://www.robotstxt.org/robotstxt.html
2 | User-agent: *
3 | Disallow:
4 |
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/src/App.css:
--------------------------------------------------------------------------------
1 | .App {
2 | text-align: center;
3 | }
4 |
5 | .App-logo {
6 | height: 40vmin;
7 | pointer-events: none;
8 | }
9 |
10 | @media (prefers-reduced-motion: no-preference) {
11 | .App-logo {
12 | animation: App-logo-spin infinite 20s linear;
13 | }
14 | }
15 |
16 | .App-header {
17 | background-color: #282c34;
18 | min-height: 100vh;
19 | display: flex;
20 | flex-direction: column;
21 | align-items: center;
22 | justify-content: center;
23 | font-size: calc(10px + 2vmin);
24 | color: white;
25 | }
26 |
27 | .App-link {
28 | color: #61dafb;
29 | }
30 |
31 | @keyframes App-logo-spin {
32 | from {
33 | transform: rotate(0deg);
34 | }
35 | to {
36 | transform: rotate(360deg);
37 | }
38 | }
39 |
--------------------------------------------------------------------------------
/src/App.js:
--------------------------------------------------------------------------------
1 | import React from 'react';
2 | import './App.css';
3 |
4 | function App() {
5 | return (
6 |
7 |
Testing Updated
8 |
9 | );
10 | }
11 |
12 |
13 | export default App;
14 |
--------------------------------------------------------------------------------
/src/App.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import {render, cleanup} from '@testing-library/react'
3 | import App from './App'
4 |
5 | describe('Take a snapshot', () => {
6 | afterEach(cleanup)
7 | it('should take a snapshot', () => {
8 | const { asFragment } = render()
9 |
10 | expect(asFragment()).toMatchSnapshot()
11 | })
12 | });
13 |
14 |
--------------------------------------------------------------------------------
/src/__snapshots__/App.test.js.snap:
--------------------------------------------------------------------------------
1 | // Jest Snapshot v1, https://goo.gl/fbAQLP
2 |
3 | exports[`Take a snapshot should take a snapshot 1`] = `
4 |
5 |
8 |
9 | Testing Updated
10 |
11 |
12 |
13 | `;
14 |
--------------------------------------------------------------------------------
/src/components/TestAsync.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 |
3 | const TestAsync = () => {
4 | const [counter, setCounter] = React.useState(0)
5 |
6 | const delayCount = () => (
7 | setTimeout(() => {
8 | setCounter(counter + 1)
9 | }, 500)
10 | )
11 |
12 | return (
13 | <>
14 | { counter }
15 |
16 |
17 |
18 | )
19 | }
20 |
21 | export default TestAsync
--------------------------------------------------------------------------------
/src/components/TestAsync.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react';
2 | import { render, cleanup, fireEvent, waitForElement } from '@testing-library/react';
3 | import TestAsync from './TestAsync'
4 |
5 | afterEach(cleanup);
6 |
7 | it('increments counter after 0.5s', async () => {
8 | const { getByTestId, getByText } = render();
9 |
10 | fireEvent.click(getByTestId('button-up'))
11 |
12 | const counter = await waitForElement(() => getByText('1'))
13 |
14 | expect(counter).toHaveTextContent('1')
15 | });
16 |
--------------------------------------------------------------------------------
/src/components/TestAxios.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import axios from 'axios'
3 |
4 | const TestAxios = ({ url }) => {
5 | const [data, setData] = React.useState()
6 |
7 | const fetchData = async () => {
8 | const response = await axios.get(url)
9 | setData(response.data.greeting)
10 | }
11 |
12 | return (
13 | <>
14 |
15 | {
16 | data ?
17 | {data}
:
18 | Loading...
19 | }
20 |
21 | )
22 |
23 | }
24 |
25 | export default TestAxios
--------------------------------------------------------------------------------
/src/components/TestAxios.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import { render, waitForElement, fireEvent } from '@testing-library/react'
3 | import axiosMock from 'axios'
4 | import TestAxios from './TestAxios'
5 |
6 | jest.mock('axios')
7 |
8 | it('should display a loading text', () => {
9 |
10 | const { getByTestId } = render()
11 |
12 | expect(getByTestId('loading')).toHaveTextContent('Loading...')
13 | })
14 |
15 | it('should load and display the data', async () => {
16 | const url = '/greeting'
17 | const { getByTestId } = render()
18 |
19 | axiosMock.get.mockResolvedValueOnce({
20 | data: { greeting: 'hello there' },
21 | })
22 |
23 | fireEvent.click(getByTestId('fetch-data'))
24 |
25 | const greetingData = await waitForElement(() => getByTestId('show-data'))
26 |
27 | expect(axiosMock.get).toHaveBeenCalledTimes(1)
28 | expect(axiosMock.get).toHaveBeenCalledWith(url)
29 | expect(greetingData).toHaveTextContent('hello there')
30 | })
--------------------------------------------------------------------------------
/src/components/TestContext.js:
--------------------------------------------------------------------------------
1 | import React from "react"
2 |
3 | export const CounterContext = React.createContext()
4 |
5 | const CounterProvider = () => {
6 | const [counter, setCounter] = React.useState(0)
7 | const increment = () => setCounter(counter + 1)
8 | const decrement = () => setCounter(counter - 1)
9 |
10 | return (
11 |
12 |
13 |
14 | )
15 | }
16 |
17 | export const Counter = () => {
18 | const { counter, increment, decrement } = React.useContext(CounterContext)
19 | return (
20 | <>
21 | { counter }
22 |
23 |
24 |
25 | )
26 | }
27 |
28 |
29 | export default CounterProvider
--------------------------------------------------------------------------------
/src/components/TestContext.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import { render, cleanup, fireEvent } from '@testing-library/react'
3 | import CounterProvider, { CounterContext, Counter } from './TestContext'
4 |
5 | const renderWithContext = (
6 | component) => {
7 | return {
8 | ...render(
9 |
10 | {component}
11 | )
12 | }
13 | }
14 |
15 | afterEach(cleanup);
16 |
17 | it('checks initial state is equal to 0', () => {
18 | const { getByTestId } = renderWithContext()
19 | expect(getByTestId('counter')).toHaveTextContent('0')
20 | })
21 |
22 | it('increments the counter', () => {
23 | const { getByTestId } = renderWithContext()
24 |
25 | fireEvent.click(getByTestId('button-up'))
26 | expect(getByTestId('counter')).toHaveTextContent('1')
27 | })
28 |
29 | it('decrements the counter', () => {
30 | const { getByTestId} = renderWithContext()
31 |
32 | fireEvent.click(getByTestId('button-down'))
33 | expect(getByTestId('counter')).toHaveTextContent('-1')
34 | })
--------------------------------------------------------------------------------
/src/components/TestElements.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 |
3 | const TestElements = () => {
4 | const [counter, setCounter] = React.useState(0)
5 |
6 | return (
7 | <>
8 | { counter }
9 |
10 |
11 |
12 | )
13 | }
14 |
15 | export default TestElements
--------------------------------------------------------------------------------
/src/components/TestElements.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react';
2 | import { render, cleanup } from '@testing-library/react';
3 | import TestElements from './TestElements'
4 |
5 | afterEach(cleanup);
6 |
7 | it('should equal to 0', () => {
8 | const { getByTestId } = render();
9 | expect(getByTestId('counter')).toHaveTextContent(0)
10 | });
11 |
12 | it('should be enabled', () => {
13 | const { getByTestId } = render();
14 | expect(getByTestId('button-up')).not.toHaveAttribute('disabled')
15 | });
16 |
17 | it('should be disabled', () => {
18 | const { getByTestId } = render();
19 | expect(getByTestId('button-down')).toBeDisabled()
20 | });
21 |
--------------------------------------------------------------------------------
/src/components/TestEvents.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 |
3 | const TestEvents = () => {
4 | const [counter, setCounter] = React.useState(0)
5 |
6 | return (
7 | <>
8 | { counter }
9 |
10 |
11 |
12 | )
13 | }
14 |
15 | export default TestEvents
--------------------------------------------------------------------------------
/src/components/TestEvents.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react';
2 | import { render, cleanup, fireEvent } from '@testing-library/react';
3 | import TestEvents from './TestEvents'
4 |
5 | afterEach(cleanup);
6 |
7 | it('increments counter', () => {
8 | const { getByTestId } = render();
9 |
10 | fireEvent.click(getByTestId('button-up'))
11 |
12 | expect(getByTestId('counter')).toHaveTextContent('1')
13 | });
14 |
15 | it('decrements counter', () => {
16 | const { getByTestId } = render();
17 |
18 | fireEvent.click(getByTestId('button-down'))
19 |
20 | expect(getByTestId('counter')).toHaveTextContent('-1')
21 | });
22 |
--------------------------------------------------------------------------------
/src/components/TestRedux.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import { connect } from 'react-redux'
3 |
4 | const TestRedux = ({counter, dispatch}) => {
5 |
6 | const increment = () => dispatch({ type: 'INCREMENT' })
7 | const decrement = () => dispatch({ type: 'DECREMENT' })
8 |
9 | return (
10 | <>
11 | { counter }
12 |
13 |
14 |
15 | )
16 | }
17 |
18 | export default connect(state => ({ counter: state.count }))(TestRedux)
--------------------------------------------------------------------------------
/src/components/TestRedux.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import { createStore } from 'redux'
3 | import { Provider } from 'react-redux'
4 | import { render, cleanup, fireEvent } from '@testing-library/react';
5 | import { initialState, reducer } from '../store/reducer'
6 | import TestRedux from './TestRedux'
7 |
8 | const renderWithRedux = (
9 | component,
10 | { initialState, store = createStore(reducer, initialState) } = {}
11 | ) => {
12 | return {
13 | ...render({component}),
14 | store,
15 | }
16 | }
17 |
18 | afterEach(cleanup);
19 |
20 | it('checks initial state is equal to 0', () => {
21 | const { getByTestId } = renderWithRedux()
22 | expect(getByTestId('counter')).toHaveTextContent('0')
23 | })
24 |
25 | it('increments the counter through redux', () => {
26 | const { getByTestId } = renderWithRedux(,
27 | {initialState: {count: 5}
28 | })
29 | fireEvent.click(getByTestId('button-up'))
30 | expect(getByTestId('counter')).toHaveTextContent('6')
31 | })
32 |
33 | it('decrements the counter through redux', () => {
34 | const { getByTestId} = renderWithRedux(, {
35 | initialState: { count: 100 },
36 | })
37 | fireEvent.click(getByTestId('button-down'))
38 | expect(getByTestId('counter')).toHaveTextContent('99')
39 | })
--------------------------------------------------------------------------------
/src/components/TestRouter.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 |
3 | import { Link, Route, Switch, useParams } from 'react-router-dom'
4 |
5 | const About = () => About page
6 |
7 | const Home = () => Home page
8 |
9 | const Contact = () => {
10 | const { name } = useParams()
11 |
12 | return {name}
13 | }
14 |
15 | const TestRouter = () => {
16 | const name = 'John Doe'
17 | return (
18 | <>
19 |
24 |
25 |
26 |
27 |
28 |
29 |
30 |
31 | )
32 | }
33 |
34 | export default TestRouter
--------------------------------------------------------------------------------
/src/components/TestRouter.test.js:
--------------------------------------------------------------------------------
1 | import React from 'react'
2 | import { Router } from 'react-router-dom'
3 | import { render, fireEvent } from '@testing-library/react'
4 | import { createMemoryHistory } from 'history'
5 | import TestRouter from './TestRouter'
6 |
7 |
8 | const renderWithRouter = (component) => {
9 | const history = createMemoryHistory()
10 | return {
11 | ...render (
12 |
13 | {component}
14 |
15 | )
16 | }
17 | }
18 |
19 | it('should render the home page', () => {
20 |
21 | const { container, getByTestId } = renderWithRouter()
22 | const navbar = getByTestId('navbar')
23 | const link = getByTestId('home-link')
24 |
25 | expect(container.innerHTML).toMatch('Home page')
26 | expect(navbar).toContainElement(link)
27 | })
28 |
29 | it('should navigate to the about page', ()=> {
30 | const { container, getByTestId } = renderWithRouter()
31 |
32 | fireEvent.click(getByTestId('about-link'))
33 |
34 | expect(container.innerHTML).toMatch('About page')
35 | })
36 |
37 | it('should navigate to the contact page with the params', ()=> {
38 | const { container, getByTestId } = renderWithRouter()
39 |
40 | fireEvent.click(getByTestId('contact-link'))
41 |
42 | expect(container.innerHTML).toMatch('John Doe')
43 | })
--------------------------------------------------------------------------------
/src/index.css:
--------------------------------------------------------------------------------
1 | body {
2 | margin: 0;
3 | font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
4 | 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
5 | sans-serif;
6 | -webkit-font-smoothing: antialiased;
7 | -moz-osx-font-smoothing: grayscale;
8 | }
9 |
10 | code {
11 | font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
12 | monospace;
13 | }
14 |
--------------------------------------------------------------------------------
/src/index.js:
--------------------------------------------------------------------------------
1 | import React from 'react';
2 | import ReactDOM from 'react-dom';
3 | import './index.css';
4 | import App from './App';
5 | import { Provider } from 'react-redux'
6 | import { createStore } from 'redux'
7 | import reducer from './store/reducer'
8 | import * as serviceWorker from './serviceWorker';
9 |
10 | const store = createStore(reducer)
11 |
12 | ReactDOM.render( , document.getElementById('root'));
13 |
14 | // If you want your app to work offline and load faster, you can change
15 | // unregister() to register() below. Note this comes with some pitfalls.
16 | // Learn more about service workers: https://bit.ly/CRA-PWA
17 | serviceWorker.unregister();
18 |
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/src/logo.svg:
--------------------------------------------------------------------------------
1 |
8 |
--------------------------------------------------------------------------------
/src/serviceWorker.js:
--------------------------------------------------------------------------------
1 | // This optional code is used to register a service worker.
2 | // register() is not called by default.
3 |
4 | // This lets the app load faster on subsequent visits in production, and gives
5 | // it offline capabilities. However, it also means that developers (and users)
6 | // will only see deployed updates on subsequent visits to a page, after all the
7 | // existing tabs open on the page have been closed, since previously cached
8 | // resources are updated in the background.
9 |
10 | // To learn more about the benefits of this model and instructions on how to
11 | // opt-in, read https://bit.ly/CRA-PWA
12 |
13 | const isLocalhost = Boolean(
14 | window.location.hostname === 'localhost' ||
15 | // [::1] is the IPv6 localhost address.
16 | window.location.hostname === '[::1]' ||
17 | // 127.0.0.0/8 are considered localhost for IPv4.
18 | window.location.hostname.match(
19 | /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
20 | )
21 | );
22 |
23 | export function register(config) {
24 | if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
25 | // The URL constructor is available in all browsers that support SW.
26 | const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
27 | if (publicUrl.origin !== window.location.origin) {
28 | // Our service worker won't work if PUBLIC_URL is on a different origin
29 | // from what our page is served on. This might happen if a CDN is used to
30 | // serve assets; see https://github.com/facebook/create-react-app/issues/2374
31 | return;
32 | }
33 |
34 | window.addEventListener('load', () => {
35 | const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
36 |
37 | if (isLocalhost) {
38 | // This is running on localhost. Let's check if a service worker still exists or not.
39 | checkValidServiceWorker(swUrl, config);
40 |
41 | // Add some additional logging to localhost, pointing developers to the
42 | // service worker/PWA documentation.
43 | navigator.serviceWorker.ready.then(() => {
44 | console.log(
45 | 'This web app is being served cache-first by a service ' +
46 | 'worker. To learn more, visit https://bit.ly/CRA-PWA'
47 | );
48 | });
49 | } else {
50 | // Is not localhost. Just register service worker
51 | registerValidSW(swUrl, config);
52 | }
53 | });
54 | }
55 | }
56 |
57 | function registerValidSW(swUrl, config) {
58 | navigator.serviceWorker
59 | .register(swUrl)
60 | .then(registration => {
61 | registration.onupdatefound = () => {
62 | const installingWorker = registration.installing;
63 | if (installingWorker == null) {
64 | return;
65 | }
66 | installingWorker.onstatechange = () => {
67 | if (installingWorker.state === 'installed') {
68 | if (navigator.serviceWorker.controller) {
69 | // At this point, the updated precached content has been fetched,
70 | // but the previous service worker will still serve the older
71 | // content until all client tabs are closed.
72 | console.log(
73 | 'New content is available and will be used when all ' +
74 | 'tabs for this page are closed. See https://bit.ly/CRA-PWA.'
75 | );
76 |
77 | // Execute callback
78 | if (config && config.onUpdate) {
79 | config.onUpdate(registration);
80 | }
81 | } else {
82 | // At this point, everything has been precached.
83 | // It's the perfect time to display a
84 | // "Content is cached for offline use." message.
85 | console.log('Content is cached for offline use.');
86 |
87 | // Execute callback
88 | if (config && config.onSuccess) {
89 | config.onSuccess(registration);
90 | }
91 | }
92 | }
93 | };
94 | };
95 | })
96 | .catch(error => {
97 | console.error('Error during service worker registration:', error);
98 | });
99 | }
100 |
101 | function checkValidServiceWorker(swUrl, config) {
102 | // Check if the service worker can be found. If it can't reload the page.
103 | fetch(swUrl, {
104 | headers: { 'Service-Worker': 'script' }
105 | })
106 | .then(response => {
107 | // Ensure service worker exists, and that we really are getting a JS file.
108 | const contentType = response.headers.get('content-type');
109 | if (
110 | response.status === 404 ||
111 | (contentType != null && contentType.indexOf('javascript') === -1)
112 | ) {
113 | // No service worker found. Probably a different app. Reload the page.
114 | navigator.serviceWorker.ready.then(registration => {
115 | registration.unregister().then(() => {
116 | window.location.reload();
117 | });
118 | });
119 | } else {
120 | // Service worker found. Proceed as normal.
121 | registerValidSW(swUrl, config);
122 | }
123 | })
124 | .catch(() => {
125 | console.log(
126 | 'No internet connection found. App is running in offline mode.'
127 | );
128 | });
129 | }
130 |
131 | export function unregister() {
132 | if ('serviceWorker' in navigator) {
133 | navigator.serviceWorker.ready
134 | .then(registration => {
135 | registration.unregister();
136 | })
137 | .catch(error => {
138 | console.error(error.message);
139 | });
140 | }
141 | }
142 |
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/src/setupTests.js:
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1 | // jest-dom adds custom jest matchers for asserting on DOM nodes.
2 | // allows you to do things like:
3 | // expect(element).toHaveTextContent(/react/i)
4 | // learn more: https://github.com/testing-library/jest-dom
5 | import '@testing-library/jest-dom/extend-expect';
6 |
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/src/store/reducer.js:
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1 | export const initialState = {
2 | count: 0,
3 | }
4 |
5 | export function reducer(state = initialState, action) {
6 | switch (action.type) {
7 | case 'INCREMENT':
8 | return {
9 | count: state.count + 1,
10 | }
11 | case 'DECREMENT':
12 | return {
13 | count: state.count - 1,
14 | }
15 | default:
16 | return state
17 | }
18 | }
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