How to use Mocha and Chai In Javascript

Mocha is a feature-rich JavaScript test framework running on the Node.js and in the browser making the asynchronous testing simple and fun. The Chai is an assertion library that pairs well with any JavaScript testing framework. Together, Mocha and Chai provide a powerful and flexible testing environment.

Syntax:

Basic syntax for a Mocha test using the Chai:

const { expect } = require('chai');
describe('description of the test suite', () => 
     {  it('description of the test', () =>
        {   
              // arrange    // act    // assert 
        }
  );
});

Implementation Code: We will use the same function add and write a unit test for it using the Mocha and Chai.

Function Code:

// math.js
function add(a, b) {
  return a + b;
}
module.exports = add;
Test Code:
// math.test.js
const add = require('./math');
const { expect } = require('chai');
describe('Addition function', () => {
    it('should add 1 and 2 to get 3', () => {
      expect(add(1, 2)).to.equal(3);
   });
});

Running the Tests:

To run the tests we need to the have Mocha and Chai installed. we can install them using npm:

npm install --save-dev mocha chai

Then, add a script to your package.json to run Mocha:

"scripts": {  "test": "mocha"}

Now you can run your tests using:

npm test

Unit testing is a crucial part of software development that helps ensure individual parts of the code work correctly. For JavaScript, unit testing can be especially valuable given the dynamic nature of the language. This guide will introduce you to the two popular approaches to unit testing in JavaScript providing the descriptions, syntax, and example implementation code.

These are the following approaches: