CODEWITHSUNDEEP
reactjsjestjsreact-hooksreact-testing-library
Vamsi
Vamsi

Reputation: 392

How to write test case by using jest for Increment using React Hooks

I am learning how to write test cases by using Jest. In my project I have a button If I Click that button then in paragraph it will show how many times I clicked. Please tell me how to write test case for that component.

This is App.js

import React from 'react';
import './App.css';
import Button from './Button/Button';

const App = () => {
  return (
    <div className='container'>
      <div className='row'>
        <div className='col-12'>
          <Button></Button>
        </div>
      </div>
    </div>
  )
}

export default App

This is Button.js

import React, { useState } from 'react';
import './Button.css';

const Button = () => {
    const [count, setCount] = useState(0);
    return (
        <div>
            <p>You clicked {count} times</p>
            <button onClick={() => setCount(count + 1)}>Increment</button>
        </div>
    )
}

export default Button

There is nothing in Button.test.js

This is package.json

{
  "name": "one",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^5.11.5",
    "@testing-library/react": "^11.1.1",
    "@testing-library/user-event": "^12.2.0",
    "react": "^17.0.1",
    "react-dom": "^17.0.1",
    "react-scripts": "4.0.0",
    "web-vitals": "^0.2.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  }
}

Upvotes: 0

Views: 1193

Answers (1)

Lin Du
Lin Du

Reputation: 102307

Unit test solution:

Button.jsx:

import React, { useState } from 'react';

const Button = () => {
  const [count, setCount] = useState(0);
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
};

export default Button;

Button.test.jsx:

import React from 'react';
import Button from './Button';
import { render, fireEvent } from '@testing-library/react';
import '@testing-library/jest-dom/extend-expect';

describe('64683116', () => {
  it('should pass', () => {
    const { container } = render(<Button></Button>);
    expect(container.querySelector('p')).toHaveTextContent('You clicked 0 times');
    expect(container.querySelector('button')).toHaveTextContent('Increment');
    fireEvent.click(container.querySelector('button'));
    expect(container.querySelector('p')).toHaveTextContent('You clicked 1 times');
    fireEvent.click(container.querySelector('button'));
    expect(container.querySelector('p')).toHaveTextContent('You clicked 2 times');
  });
});

unit test result:

 PASS  examples/64683116/Button.test.jsx
  64683116
    ✓ should pass (27 ms)

------------|---------|----------|---------|---------|-------------------
File        | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
------------|---------|----------|---------|---------|-------------------
All files   |     100 |      100 |     100 |     100 |                   
 Button.jsx |     100 |      100 |     100 |     100 |                   
------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        5.68 s

source code: https://github.com/mrdulin/jest-v26-codelab/tree/main/examples/64683116

Upvotes: 3

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