Mastering Jest: A Guide to Efficient JavaScript Testing

Jest is a popular javascript testing framework (also known as jest is open sourch testing framework) designed to ensure correctness of any codebase. it allows you to write test with an approchable familiar and featured-rich API that gives you result quickly. jest is well-documented, reqiuires lottle configuration and can be extended to match your requirments.

Key Features of Jest:

zero configuration: jest work out of the box with minimal setup.
Fast and effecient: parralel test execution speeds up tetsing process.
Snapshot testing: compare and capture UI Snapshot.
Built-in Mocks and spies: Simplyfies mocking dependencies.
Code Coverage: generate detailed code reports.
Extenshive community Supports: a large ecosystem of plugins and tools.

Installing Jest
you can install jest in your project using nom or yarn.

# using npm
npm install --save-dev jest

$ using yarn
yarn add -dev jest

For typescript Projects, also install the types:

npm install --save-dev @types/jest

Writing Your first Test
create a new file, sum.test.js, in your projrct

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

// sum.test.js
const sum = require('./sum');

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

Run the test using:

npx jest

If everything is set up correctly, Jest will output:

PASS  ./sum.test.js
  ✓ adds 1 + 2 to equal 3