Node.js Testing - Search localsearch

jestjs.io

https://jestjs.io/

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It works with projects using: Babel, TypeScript, Node, React, Angular, Vue and more!

jestjs.io

https://jestjs.io/docs/getting-started

Getting Started - Jest

Let's get started by writing a test for a hypothetical function that adds two numbers. First, create a sum.js file:

jestjs.io

https://jestjs.io/docs/asynchronous

Testing Asynchronous Code · Jest

It's common in JavaScript for code to run asynchronously. When you have code that runs asynchronously, Jest needs to know when the code it is testing has completed, before it can move on to another test. Jest has several ways to handle this.

jestjs.io

https://jestjs.io/docs/tutorial-react

Testing React Apps · Jest

See React: Function and Class Components. Reminders that with Class components, we expect Jest to be used to test props and not methods directly. Now let's use React's test renderer and Jest's snapshot feature to interact with the component and capture the rendered output and create a snapshot file:

jestjs.io

https://jestjs.io/docs/expect

Expect - Jest

Since you are still testing promises, the test is still asynchronous. Hence, you will need to tell Jest to wait by returning the unwrapped assertion. Alternatively, you can use async/await in combination with .rejects.

jestjs.io

https://jestjs.io/docs/ecmascript-modules

ECMAScript Modules · Jest

import {jest, test} from '@jest/globals'; test('test esm-module', async () => { jest.unstable_mockModule('./esm-module.js', () => ({ default: () => 'default implementation', namedFn: () => 'namedFn implementation', })); const mockModule = await import('./esm-module.js'); console.log(mockModule.default()); // 'default implementation'

jestjs.io

https://jestjs.io/docs/testing-frameworks

Testing Web Frameworks · Jest

Jest is a universal testing platform, with the ability to adapt to any JavaScript library or framework. In this section, we'd like to link to community posts and articles about integrating Jest into popular JS libraries.

jestjs.io

https://jestjs.io/docs/api

Globals - Jest

In your test files, Jest puts each of these methods and objects into the global environment. You don't have to require or import anything to use them. However, if you prefer explicit imports, you can do import {describe, expect, test} from '@jest/globals'.

jestjs.io

https://jestjs.io/docs/snapshot-testing

Snapshot Testing · Jest

More information on how snapshot testing works and why we built it can be found on the release blog post. We recommend reading this blog post to get a good sense of when you should use snapshot testing. We also recommend watching this egghead video on Snapshot Testing with Jest.

jestjs.io

https://jestjs.io/docs/setup-teardown

Setup and Teardown - Jest

If a test is failing, one of the first things to check should be whether the test is failing when it's the only test that runs. To run only one test with Jest, temporarily change that test command to a test.only: