Creating Unit Tests For Your Node.js Projects Using Mocha

While working on any JavaScript project, it is important to write tests for your project features/components as much as it is important to create the project features themselves.

Unit testing in Node.js is a process where by the developer in charge of a project creates a module that helps to test whether a feature that was added in the project was working as it should be.

Most of the time, unit tests are usually performed on individual functions of a feature or project and each function/feature is referred to as a unit.

Node.js provides an easy way for developers to create unit tests for their project features through a very effective package known as Mocha.

Mocha.js is a wonderful JavaScript test framework with wonderful features that helps to simplify the process of unit testing.

Using Mocha

In order to use Mocha to create unit tests in your projects, you need to install the package.

To install Mocha, run this command in your project terminal

npm install mocha

Moving forward, we are going to create a new directory in the root directory of our project and name it test.

In the test directory, create a file new.test.js.

Now, we are going to test a function in the file to show how Mocha works.

We are going to use a npm package to run a test that checks whether the square root of any passed value is returning the correct data.

Let;s install the package by running the command

npm install mathjs

in new.test.js add the following code

const { sqrt } = require('mathjs')
const  assert = require('assert');

describe('Square root Test', () => {
    it('should return 2', () => {
        assert.equal(sqrt(4).toString(), 2);
    });
    it('should return 3', () => {   
        assert.equal(sqrt(9).toString(), 3);
    });
});

In package.json, add this in your scripts object

"test": "mocha"

In your terminal, run the command npm run test in order to run the test we created

If the function we tested in returning the correct data, we should see the following result in the terminal log

enter image description here

If the function had failed, which it would have had we passed the wrong data such as in the example below

const { sqrt } = require('mathjs')
const  assert = require('assert');

describe('Square root Test', () => {
    it('should return 3', () => {
        assert.equal(sqrt(4).toString(), 3);
    });
    it('should return 12', () => {  
        assert.equal(sqrt(9).toString(), 12);
    });
});