Is Jest faster than Karma?

Jest is two to three times faster than Karma for testing purposes. We should take special notes while defining CI/CD pipeline since the test execution time will be faster.

Can Jest Run Jasmine test?

If you use Jasmine or Jasmine like APIs such as mocha. Jest should be mostly compatible, making it less complicated to migrate to js.

What is Karma in Angular?

Karma is the test feature of the Angular framework. They are the default test runner for the application created in Angular CLI.

What is code coverage in Angular?

Code coverage reports show you any areas of your codebase that your unit tests haven't thoroughly tested. Run it in your browser, run it in your browser, or download and run it locally, download and run it locally if you want to play around with the programme described in this guide.

Table of contents

Introduction

Setting up Dependencies

Configuring Jest

3.1.

Create the jest.config.js in the root directory

3.2.

Update src/test.ts file

3.3.

Update tsconfig.spec.json file

3.4.

Remove comments in the ts config files

3.5.

Run the tests

Remove Karma

4.1.

Removing dependencies

4.2.

Removing karama.config.json

4.3.

Removing the test target inside the angular.json file

FAQs

Key Takeaways

Last Updated: Mar 27, 2024

Jest Testing Environment in Angular

Author Aman Thakur

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Introduction

Angular comes with a pre-installed unit testing framework such as Jasmine and Karma. But in this article, we will discuss how to ditch them, i.e., you can use Jest instead of them. So, let's get started.

Setting up Dependencies

Let's get started with installing the needed dependencies:

If you are using npm,

npm install jest jest-preset-angular @types/jest --save-dev

If you are using yarn,

yarn add jest jest-preset-angular @types/jest --dev

Configuring Jest

Create a new project named myapp using the command given below:

ng new my-app

Create the jest.config.js in the root directory

const { pathsToModuleNameMapper } = require("ts-jest/utils");
const { compilerOptions } = require("./tsconfig");

module.exports = {
	preset: "jest-preset-angular",
	roots: ["<rootDir>/src/"],
	testMatch: ["**/+(*.)+(spec).+(ts)"],
	setupFilesAfterEnv: ["<rootDir>/src/test.ts"],
	collectCoverage: true,
	coverageReporters: ["html"],
	coverageDirectory: "coverage/my-app",
	moduleNameMapper: pathsToModuleNameMapper(compilerOptions.paths || {}, {
  	prefix: "<rootDir>/",
	}),
};

You can also try this code with Online Javascript Compiler

Run Code

Update src/test.ts file

import 'jest-preset-angular/setup-jest';

Object.defineProperty(window, 'CSS', { value: null });


Object.defineProperty(window, 'getComputedStyle', {
value: () => {
  return {
    display: 'none',
    appearance: ['-webkit-appearance'],
  };
},
});

Object.defineProperty(document, 'doctype', {
value: '<!DOCTYPE html>',
});

Object.defineProperty(document.body.style, 'transform', {
value: () => {
  return {
    enumerable: true,
    configurable: true,
  };
},
});

You can also try this code with Online Javascript Compiler

Run Code

Update tsconfig.spec.json file

{
"extends": "./tsconfig.json",
"compilerOptions": {
  "outDir": "./out-tsc/spec",
  "types": [
    "jest", // 1
    "node"
  ],
  "esModuleInterop": true, // 2
  "emitDecoratorMetadata": true // 3
},
"files": ["src/test.ts", "src/polyfills.ts"],
"include": ["src/**/*.spec.ts", "src/**/*.d.ts"]
}

You can also try this code with Online Javascript Compiler

Run Code

Remove comments in the ts config files

Open the tsconfig.json and tsconfig.spec.json and delete the comment in the first line.

Run the tests

Go to the terminal and just run npx jest.

Remove Karma

Removing dependencies

For npm

npm uninstall karma karma-chrome-launcher karma-coverage-istanbul-reporter karma-jasmine

You can also try this code with Online Javascript Compiler

Run Code

Or for yarn

yarn remove karma karma-chrome-launcher karma-coverage-istanbul-reporter karma-jasmine karma-jasmine-html-reporter

Removing karama.config.json

rm karma.conf.js

Removing the test target inside the angular.json file

"test": {
  "builder": "@angular-devkit/build-angular:karma",
  "options": {
    "main": "src/test.ts",
    "polyfills": "src/polyfills.ts",
    "tsConfig": "tsconfig.spec.json",
    "karmaConfig": "karma.conf.js",
    "assets": [
      "src/favicon.ico",
      "src/assets"
    ],
    "styles": [
      "src/styles.css"
    ],
    "scripts": []
  }
}

You can also try this code with Online Javascript Compiler

Run Code

FAQs

Is Jest faster than Karma?
Jest is two to three times faster than Karma for testing purposes. We should take special notes while defining CI/CD pipeline since the test execution time will be faster.
Can Jest Run Jasmine test?
If you use Jasmine or Jasmine like APIs such as mocha. Jest should be mostly compatible, making it less complicated to migrate to js.
What is Karma in Angular?
Karma is the test feature of the Angular framework. They are the default test runner for the application created in Angular CLI.
What is code coverage in Angular?
Code coverage reports show you any areas of your codebase that your unit tests haven't thoroughly tested. Run it in your browser, run it in your browser, or download and run it locally, download and run it locally if you want to play around with the programme described in this guide.

Key Takeaways

This article covers essential details of setting up the testing environment in Jest. We have set up the configuration file in jest and edited files wherever necessary for setting up the environment by modifying a few other configuration files.

Hence never stop your journey of learning. Here are some of the links you might be interested in, such as Getting started with Jest, Mocking in Jest, Matchers in Jest.

Happy Learning!

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