KaneAI - World’s First E2E Software Testing Agent.Signup for Private Beta Join TestMu Conference

How to use __setCpus method in Jest

Best JavaScript code snippet using jest

getMaxWorkers.test.js

Source:getMaxWorkers.test.js

...8import getMaxWorkers from '../getMaxWorkers';9jest.mock('os');10describe('getMaxWorkers', () => {11  beforeEach(() => {12    require('os').__setCpus({length: 4});13  });14  it('Returns 1 when runInBand', () => {15    const argv = {runInBand: true};16    expect(getMaxWorkers(argv)).toBe(1);17  });18  it('Returns 1 when the OS CPUs are not available', () => {19    require('os').__setCpus(undefined);20    expect(getMaxWorkers({})).toBe(1);21  });22  it('Returns the `maxWorkers` when specified', () => {23    const argv = {maxWorkers: 8};24    expect(getMaxWorkers(argv)).toBe(8);25  });26  it('Returns based on the number of cpus', () => {27    expect(getMaxWorkers({})).toBe(3);28    expect(getMaxWorkers({watch: true})).toBe(2);29  });...

os.js

Source:os.js

...6 */7'use strict';8const os = jest.genMockFromModule('os');9let cpus;10function __setCpus(newCpus) {11  cpus = newCpus;12}13os.__setCpus = __setCpus;14os.cpus = jest.fn(() => cpus);...

48os.js

Source:48os.js

...6 */7'use strict';8const os = jest.genMockFromModule('os');9let cpus;10function __setCpus(newCpus) {11  cpus = newCpus;12}13os.__setCpus = __setCpus;14os.cpus = jest.fn(() => cpus);...

Jest Testing Tutorial

LambdaTest’s Jest Testing Tutorial covers step-by-step guides around Jest with code examples to help you be proficient with the Jest framework. The Jest tutorial has chapters to help you learn right from the basics of Jest framework to code-based tutorials around testing react apps with Jest, perform snapshot testing, import ES modules and more.

Chapters

What is Jest Framework
Advantages of Jest - Jest has 3,898,000 GitHub repositories, as mentioned on its official website. Learn what makes Jest special and why Jest has gained popularity among the testing and developer community.
Jest Installation - All the prerequisites and set up steps needed to help you start Jest automation testing.
Using Jest with NodeJS Project - Learn how to leverage Jest framework to automate testing using a NodeJS Project.
Writing First Test for Jest Framework - Get started with code-based tutorial to help you write and execute your first Jest framework testing script.
Jest Vocabulary - Learn the industry renowned and official jargons of the Jest framework by digging deep into the Jest vocabulary.
Unit Testing with Jest - Step-by-step tutorial to help you execute unit testing with Jest framework.
Jest Basics - Learn about the most pivotal and basic features which makes Jest special.
Jest Parameterized Tests - Avoid code duplication and fasten automation testing with Jest using parameterized tests. Parameterization allows you to trigger the same test scenario over different test configurations by incorporating parameters.
Jest Matchers - Enforce assertions better with the help of matchers. Matchers help you compare the actual output with the expected one. Here is an example to see if the object is acquired from the correct class or not. -

|it('check_object_of_Car', () => { expect(newCar()).toBeInstanceOf(Car); });| | :- |

Jest Hooks: Setup and Teardown - Learn how to set up conditions which needs to be followed by the test execution and incorporate a tear down function to free resources after the execution is complete.
Jest Code Coverage - Unsure there is no code left unchecked in your application. Jest gives a specific flag called --coverage to help you generate code coverage.
HTML Report Generation - Learn how to create a comprehensive HTML report based on your Jest test execution.
Testing React app using Jest Framework - Learn how to test your react web-application with Jest framework in this detailed Jest tutorial.
Test using LambdaTest cloud Selenium Grid - Run your Jest testing script over LambdaTest cloud-based platform and leverage parallel testing to help trim down your test execution time.
Snapshot Testing for React Front Ends - Capture screenshots of your react based web-application and compare them automatically for visual anomalies with the help of Jest tutorial.
Bonus: Import ES modules with Jest - ES modules are also known as ECMAScript modules. Learn how to best use them by importing in your Jest testing scripts.
Jest vs Mocha vs Jasmine - Learn the key differences between the most popular JavaScript-based testing frameworks i.e. Jest, Mocha, and Jasmine.
Jest FAQs(Frequently Asked Questions) - Explore the most commonly asked questions around Jest framework, with their answers.