Do you wish to write tests for your code independently? If so, then you’ve landed in the right place. In this comprehensive Jest testing tutorial, we’ll help you learn and do it in one of the fastest ways; yes, it’s Jest Testing.

Designed for unit testing JavaScript and React code, Jest is compatible with projects using aBbel, TypeScript, Node, Angular, Vue, and more. Jest requires zero configuration, allows Snapshot Testing, and runs parallel tests in a sandboxed environment."

With Jest unit testing, you can write reliable and maintainable tests for your applications. Jest’s powerful mocking capabilities allow you to isolate the code you are testing, ensuring that your tests run consistently. It also provides a rich API for creating test suites, including support for asynchronous tests, making it ideal for modern JavaScript applications for which you should learn JavaScript too.

Additionally, Jest’s CLI offers a simple and intuitive way to run your tests and generate detailed reports. The framework also includes features like code coverage analysis and integration with various CI/CD pipelines, helping you maintain high code quality and ensure that your application works as expected.

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Well, this is just the start! Today, we will guide you through the essentials of Jest unit testing. From installation and configuration to writing and executing your first tests, this jest tutorial covers the basics to advance concepts of jest testing. We will talk about what is Jest framework, its main characteristics and features, and a detailed approach to starting with the Jest test as a beginner. In the later part, we talk about the salaries of developers with Jest testing competencies. So, stay tuned with us through to the end

Let’s start with understanding what is Jest, as a framework.

What is Jest Framework?

Jest is one of the leading frameworks for unit testing in JavaScript. It was created by Facebook (now “Meta”) for their internal testing for React components in 2011. Later, in 2014, Meta released Jest as an open-source testing framework. 

Soon after its public release, Jest became popular among developers for the advantages it offers. The popularity of Jest is well defined by the huge download numbers and its use in public repositories. There were around 300+ million Jest downloads in the last month and used over 11,000,000 public repositories on GitHub.  

Though created for unit testing React components, jest is used for testing both front-end and back-end JavaScript applications. It’s a framework, which means it provides a complete setup for testing rather than just individual pieces. 

Let’s now move on to exploring the main characteristics of Jest in the next section.

Main characteristics of Jest

Jest testing is popular for many reasons. These are the characteristics that make it unique and user-friendly. Here’s a brief explanation of the key characteristics of the Jest testing framework.

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1. Zero Configuration: Setting up Jest is easy and fast. It assumes sensible defaults, saving considerable time in tweaking configuration and reading lengthy documents. When you create a new project and install Jest (via npm or yarn), it’s ready to roll. You write your tests, run npm jest, and Jest handles the rest.

2. Command Line Interface: Jest includes a Command Line Interface (CLI) that allows you to run commands directly from the terminal. It also includes an assertion library to check if the conditions in your tests are met.  

3. Built-in Code Coverage: The built-in code coverage shows you reports of what files are not covered in your code, making Jest extremely handy when writing tests and helping you to ensure everything is covered.

4. Snapshot Testing: Snapshot Testing allows you to capture the output of components and compare them to previous outputs.

5. Mocks and Spies: The built-in Mocking library allows you to mock any object outside your test scope and spy on function calls.

6. Sandboxed Parallel Testing: Jest executes all tests in an isolated environment, allowing you to run multiple parallel tests. 

7. Great API: Jest offers a well-segregated toolkit to help you fetch and use while testing. These include various “matchers” that you may need to get returns. All you need is to land on the documentation page on the Jest official website and explore the API section.

How to get started with testing using Jest

Testing using Jest is straightforward, especially with its minimal configuration requirements. Let’s see how to get started with Jest testing in a step-by-step chronology below.

Step 1: Install Node.js and npm

Before you begin,  you do need to have node.js installed so we can use npm. If you do not have one, please download it from  Node.js official website. Once you have node installed you can check the version by typing:

$node-v

This will give you the version of the node you installed.

Step 2: Set Up Your Project

Initialize npm: 

Before we move on to installing Jest. we need to initiate npm first. To do that simply type:

$ npm init -y

This will create a package.jason. Currently, we have no dependencies whatsoever. Let’s move on to installing Jest with dev dependencies.

Step 3: Install Jest

Install Jest as a development dependency in your project. Jest as dev dependency is important as we run tests only during developments. 

npm install --save-dev jest

If you open package.jason, you will see Jest under dev dependency. 

Step 4: Configure Jest

Add a test script to your package.json file to run Jest. Initially, you will have some different scripts there. Replace the texts after the test with “Jest.” That’s the only configuration you need to do with Jest Testing Framework. Doing this will define our test script.

{

  "scripts": {

    "test": "jest"

  }

}

Now let’s move to writing your first.

Step 5: Write Your First Test

Create a test file: Jest will look for files with .test.js or .spec.js extensions by default. Create a file named sum.test.js.

touch sum.test.j

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