Which Three Items Are Assertion Libraries For Javascript Test Automation

Which Three Items Are Assertion Libraries For Javascript Test Automation

5 min read Jun 18, 2024
Which Three Items Are Assertion Libraries For Javascript Test Automation

Which Three Items Are Assertion Libraries for Javascript Test Automation?

When writing automated tests for your Javascript code, assertion libraries play a crucial role in verifying the expected behavior of your application. They provide a structured and readable way to express your expectations and make test results clear and concise.

Here are three popular assertion libraries for Javascript test automation:

1. Chai

Chai is a highly versatile and flexible assertion library. It offers a range of assertion styles, including:

  • Expect: A BDD-style (Behavior Driven Development) syntax that emphasizes readability.
  • Should: A more traditional, object-oriented approach.
  • Assert: A more traditional, function-based approach.

Chai integrates seamlessly with other Javascript testing frameworks like Mocha, Jasmine, and Jest, making it a popular choice for various testing scenarios.

Key Features:

  • Multiple Assertion Styles: Provides flexibility to choose the style that suits your testing needs.
  • Chainable Assertions: Allows for creating concise and readable assertion chains.
  • Custom Assertions: Offers the ability to define your own custom assertions for specific needs.


const expect = require('chai').expect;

describe('My Function', () => {
  it('should return the correct value', () => {
    const result = myFunction(10);

2. Jest

Jest is a powerful testing framework by Facebook, built-in with a comprehensive assertion library. Jest's assertion library provides a straightforward and user-friendly syntax for writing tests.

Key Features:

  • Built-in Assertions: Offers a wide range of assertions for various testing scenarios, including equality, truthiness, and object properties.
  • Snapshot Testing: Captures the expected output of components or functions and automatically verifies future changes.
  • Mocking: Allows for creating mock objects to isolate and test specific parts of your code.


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

test('object assignment', () => {
  const data = {one: 1};
  expect(data).toEqual({one: 1});

3. Jasmine

Jasmine is a behavior-driven development framework with its own built-in assertion library. While primarily known for its testing framework, it provides a robust set of assertions for verifying test expectations.

Key Features:

  • Readable Syntax: Utilizes a BDD-style syntax for writing test descriptions and expectations.
  • Built-in Assertions: Offers a range of assertions, including equality, truthiness, and array/object property checks.
  • Custom Matchers: Allows for defining custom matchers to extend the assertion capabilities.


describe('My Function', function() {
  it('should return the correct value', function() {

Choosing the Right Assertion Library:

The best choice for you depends on your project's needs and preferences. If you're already using Jest or Jasmine, their built-in assertion libraries provide a seamless integration. If you're looking for more flexibility and customization, Chai offers a wide range of options.