Getting started with front-end unit testing Jest

1. Installation dependencies

npm install jest -g

2. js code

main.js

function sum(a, b) {
    
    
    return a + b;
}
module.exports = sum;

3. Test case code

main.test.js

const main = require('./main');
 
test('adds 1 + 2 to equal 3', () => {
    
    
  expect(main(1, 2)).toBe(3);
});

4. Execution

jest main

The test fails
main.test.js

const main = require('./main');
 
test('adds 1 + 2 to equal 4', () => {
    
    
  expect(main(1, 2)).toBe(4);
});