@jest/expect-utils

What is @jest/expect-utils?

@jest/expect-utils is a utility package for Jest that provides additional matchers and utilities to enhance the testing experience. It is designed to work seamlessly with Jest's built-in expect function, allowing for more expressive and readable test assertions.

What are @jest/expect-utils's main functionalities?

toBeArray

Checks if the value is an array.

expect([1, 2, 3]).toBeArray();

toBeObject

Checks if the value is an object.

expect({ key: 'value' }).toBeObject();

toBeEmpty

Checks if the value is empty. This can be used for arrays, objects, or strings.

expect([]).toBeEmpty();

toContainKey

Checks if the object contains the specified key.

expect({ key: 'value' }).toContainKey('key');

toContainValue

Checks if the object contains the specified value.

expect({ key: 'value' }).toContainValue('value');

Other packages similar to @jest/expect-utils

jest-extended

jest-extended provides a large number of additional matchers for Jest. It offers a wide range of matchers similar to @jest/expect-utils, such as toBeArray, toBeObject, and toBeEmpty, but also includes many more specialized matchers.

chai

Chai is an assertion library for Node.js and the browser that can be paired with any testing framework. It provides a rich set of matchers and is highly extensible. While it is not specifically designed for Jest, it offers similar functionalities through its expect/should interfaces.

expect-more

expect-more is a set of additional matchers for Jest and Jasmine. It provides a variety of matchers for different data types and use cases, similar to @jest/expect-utils, and aims to make tests more expressive and readable.

README

@jest/expect-utils

This module exports some utils for the expect function used in Jest.

You probably don't want to use this package directly. E.g. if you're writing custom matcher, you should use the injected this.equals.