Jest-Unexpected

This library provides a mapping layer allowing assertions using Jest expect API to execute via Unexpected and leverage it's output capabilities.

Jest-Unexpected aims to be a drop-in such that using it within an existing test suite is as simple as npm install jest-unexpected and adding a require:

const expect = require('jest-unexpected');

describe('a null value', () => {
    it('should equal null', () => {
        expect(null).toEqual(null);
    });
});

Read the documentation.

Browser

Unexpected has full browser support which is inherited by Jest-Unexpected. The library fully executes in the browser, and a demonstration of this is available in the examples folder or interactively by checking out this repository and executing:

$ npm install
$ npm start

Compatibility

Almost the entirety of Jest expect API in implemented with only the following missing methods which the library will highlight during execution (an exception will be thrown with a clear message indicating the method name):

• snapshot related functionality
  • toMatchSnapshot()
  • toThrowErrorMatchingSnapshot()
  • expect.addSnapshotSerializer()
• extension related functionality
  • expect.extend()

This library supports and is tested against node version 14 and above and the API supported is at the level of expect exposed by jest version 27.0.

For compatibility with older node versions, browsers and IE11 please make use of version 2.x of the library.

Output

Unexpected has very powerful output capabilities with features such as inline diff rendering for complex objects and an emphasis on being able to rapidly locate issues and provide hints as to corrections.

The examples included here showcase some of these differences via comparisons.

Array containing string and regex members