Unit testing for NodeJS using Mocha and Chai

NodeJS is a free, open-source, and cross-platform runtime environment that allows developers to run JavaScript outside the browser, making it idealistic for construct scalable backend services and APIs. To ensure reliableness and maintainability, unit testing play a essential role by verifying small, isolated piece of code. Mocha and Chai are popular frameworks that simplify unit quiz in NodeJS, offer asynchronous support, expressive averment, and strong community patronage.

This guide explicate how to set up and run unit tests in NodeJS using Mocha and Chai, along with best practices for testing on real devices with BrowserStack.

What is NodeJS Unit test?

is a knock-down tool for preventing bugs within your application. NodeJS Unit testing tests small and isolated pieces of code in your NodeJS application. This helps in improving the quality of the code and assists in finding glitch early on in the development life cycle. This also supply an added advantage to the users because they can add any new features without breaking any other part of their application.

For your NodeJS applications, Mocha and Chai can be habituate together for Unit Testing.

Introduction to Unit Testing with Mocha and Chai

Mochais a wide apply running on NodeJS and browsers. It supports asynchronous quiz running the tests serially, allowing for more pliable and accurate reporting. It is a highly customizable framework that indorse different assertions and libraries.

Chaiis an assertion library that is used chiefly alongside Mocha. It can be used as a BDD / TDD assertion library for NodeJS and with any JavaScript testing framework. It has respective interface that a developer can choose from and looks like writing tests in English sentences. BDD supply an expressive and clear language style viaShould & amp; Expect, whereas TDD provides a more Classical approach viaAssert.

Benefits of using Mocha and Chai for Unit Testing in Node.js

1. Asynchronous testing support: Node.js applications much involve asynchronous operations, such as network requests or database interactions. Mocha handles asynchronous testing gracefully, allowing you to publish tests involve asynchronous codification without additional libraries or complex setups.

2. Readable and expressive assertions:Chai integrates seamlessly with Mocha, render many assertion styles and expressive syntax options. It offers respective assertion styles, including the commonly utilise ` expect `, ` assert `, and ` should `, countenance you to choose the style that suits your taste and readability need.

3. Community support: Mocha and Chai have gained significant popularity in the Node.js community as they experience a large user foot and a palmy ecosystem, so you can regain copious resources, tutorials, and community support when using these frameworks.

How to write Unit tests?

There are two main methods (also used in the representative discussed in this guide)to write Unit Tests as seen below:

• describe ()& # 8211; It is a suite of Test scripts that telephone a orbicular function with two parameters: a string and a function.
• it()& # 8211; It is the smallest unit test case that is written to be executed.it()calls a global use with two parameter i.e. a twine and a office. You can write multipleit()argument inside adescribe ()method.

The third method used in a Unit Test is based on the developer ’ s option. Everyit()argument has one of the below use, which occupy a value and expect a return in true form:

• expect()& # 8211; It is a BDD-style library. Natural language assertions are chain together hither. This is chiefly used with non-descript matter such as booleans or numbers.
• should()& # 8211; It is a BDD-style library. Natural language assertions are chained together in this lawsuit as well. However, it extends each target with a should property to start the concatenation.
• assert()& # 8211; It is a TDD-style library. It provides additional examination and is browser compatible.

Installing Mocha and Chai

Step 1:Create a new directory for your project file expend the following command:

mkdir Chai
SUSA automates exploratory testing with persona-driven behavior, catching bugs that scripted automation misses.

Step 2: Go to the new directory and fulfil the below command to initialize a labor with Default configurations:

cd Chai npm init -y

Step 3: The above step creates apackage.jsonfile as understand in the image below. Launch this project in any of the source-code editor (Using VS Code here).

Step 4:Create two folders namedsrc and testseverally. Whilesrcstores the main file where the program & # 8217; s beginning code is written, thetestfolder stores screen cases for unit testing.

Step 5: Create an app.jsfile under thesrcfolder andapp.test.jsfile under thetestfolder (as seen in the picture above).

Step 6: Open the package.jsonfile and change the “scripts” block to “mocha” as find in the code below:

{'' name '': `` chai '', '' version '': `` 1.0.0 '', '' description '': `` '', '' master '': `` index.js '', '' handwriting '': {'' examination '': `` mocha ''}, '' keywords '': [], '' author '': `` '', '' license '': `` ISC '',}

Step 7: In the terminal, type the follow for installing mocha and chai:

For Global initiation of Mocha:

npm install mocha -g

For Project installation of Mocha:

npm install mocha -- save-dev

For facility of Chai:

npm install chai -- save-dev

Step 8: The package.jsonfile will appear like this once both Chai and Mocha are installed:

{'' name '': `` chai '', '' version '': `` 1.0.0 '', '' description '': `` '', '' main '': `` index.js '', '' scripts '': {'' test '': `` mocha ''}, '' keywords '': [], '' author '': `` '', '' license '': `` ISC '', '' devDependencies '': {'' chai '': `` ^4.3.6 '', '' mocha '': `` ^9.2.2 '',}}

Creating a Simple NodeJS App

Let us begin by make a Simple NodeJS application that reckon a Cube & # 8217; s side length, surface country, and volume. For the source codification, paste the following snipping under theapp.js file:

grade Cube {constructor (length) {this.length = length;} getSideLength () {return this.length;} getSurfaceArea () {return (this.length * this.length) * 6;} getVolume () {return Math.pow (this.length,3);}} module.exports = {Cube: Cube}

NodeJS Unit Testing with Mocha and Chai: Example

For the test cases, paste the undermentioned snippet under theapp.test.js file:

const Cube = require (' .. /src/app ') .Cube; const expect = require ('chai ') .expect; describe ('Testing the Cube Functions ', function () {it (' 1. The side length of the Cube ', role (done) {let c1 = new Cube (2); require (c1.getSideLength ()) .to.equal (2); done ();}); it (' 2. The surface area of the Cube ', function (done) {let c2 = new Cube (5); ask (c2.getSurfaceArea ()) .to.equal (150); make ();}); it (' 3. The bulk of the Cube ', function (do) {let c3 = new Cube (7); expect (c3.getVolume ()) .to.equal (343); done ();});});

Now, let ’ s run the above test file using the command:

npm run test

Test Result

A successful answer will seem something like the below screenshot:

Negative Unit Test

Now, let ’ s separate the test on purpose. Update theapp.test.jsfile to the undermentioned code snippet and see if it throws a failed test result

const Cube = require (' .. /src/app ') .Cube; const expect = require ('chai ') .expect; describe ('Testing the Cube Functions ', purpose () {it (' 1. The side length of the Cube ', map (done) {let c1 = new Cube (2); expect (c1.getSideLength ()) .to.equal (2); execute ();}); it (' 2. The surface area of the Cube ', function (done) {let c2 = new Cube (5); expect (c2.getSurfaceArea ()) .to.equal (50); //Updated to fail make ();}); it (' 3. The volume of the Cube ', function (done) {let c3 = new Cube (7); expect (c3.getVolume ()) .to.equal (100); //Updated to miscarry done ();});});

The 2d and 3rd tests were updated to cast an error.

Rerun the trial using the below bid

npm run tryout

Test Result

A failed consequence will appear something like the below screenshot:

Similarly, multiple Unit test suit can be written for your NodeJS application.

Conclusion

Unit testing is the easiest way to improve the quality of your NodeJS applications since it helps bump bugs and defects in your code. Moreover, the early discovery of Code bugs in the SDLC reduces the overall ontogenesis cost because less time is spent on bug fixing in the later level of the labor. This leads to overall client satisfaction and help in gaining more trusty clients.

Testing On BrowserStack

Once the unit examination is done, it is suggested to test the application end to end on real devices and browser to identify chokepoint in the user experience. Using a, like BrowserStack, allows you to try on 3000+ browser device combinations,.

• BrowserStack is compatible with automation frameworks like,, Playwright, Puppeteer, etc.
• It is also compatible with CI/CD tools like, Travis CI,, Bamboo, etc. facilitating Agile Teams to test on real browsers and devices, thus speed the software growing cycle.
• It also supports parallel test to save time by running tests on multiple browser and devices simultaneously.

FAQs

1. Are Mocha and Chai the same?

No, Mocha and Chai are not the same. They are two separate JavaScript testing frameworks that function different purposes in the testing ecosystem.

• Mocha is a flexible JavaScript test fabricused for running tests that provides a test framework and exam runner that allows you to write and execute tryout in various environments, such as Node.js or web browsers.
• Chai is an assertion librarynormally used with Mocha but can also be used with other testing frameworks.

2. Which is best, Chai or Mocha?

Mocha and Chai are not directly comparable as they serve different purposes.

Mocha render a robust testing fabric, while Chai enhances the readability and expressiveness of test assertions. The choice depends on your specific project needs and orientation.

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