JavaScript :: Testing :: Jest :: Courses :: JavaScript Unit Testing with Jest :: 2. Writing Your First Unit Test with Jest

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JavaScript :: Testing :: Jest :: Courses :: JavaScript Unit Testing with Jest :: 2. Writing Your First Unit Test with Jest

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Course Intro

Version Check

• JavaScript 2022
• Jest v29
• Node.js v18
• npm v8

Why Write Unit Tests?

• Manual testing takes too much time
• Unit tests can be run automatically
• Give us confidence in the quality of our source code
• Can facilitate Test-Driven Development (TDD)
• Can act like documentation

Test Pyramid

• E2E Tests
• Integeration Tests
• Unit Tests

Overview

• Why are unit tests so important?
• Jest installation
• Writing basic unit tests with Jest
• Using common matchers
• Using mocks
• Testing asyncronous functions
• Measuring code coverage

Getting Started with Jest

Key Benefits of Using Jest

• No configuration required to get started
• Highly intuitive API
• Runs test in parallel
• Works with the vast majority of JS projects
• Great documentation and a large community

Install Jest

» npm install jest --save-dev

test Pacakage Script

add "jest" to the test script

» npm test

Writing a Simple Unit Test

test

Parameters

• name: Test's Name
• fn: Test Function
• timeout: The timeout for an async function test

expect(actual)

The argument for the expect function is the value that you want to validate (actual)

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