@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');

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Changelog

Source

29.7.0

Features

[create-jest] Add npm init / yarn create initialiser for Jest projects (#14465)
[jest-validate] Allow deprecation warnings for unknown options (#14499)

Fixes

[jest-resolver] Replace unmatched capture groups in moduleNameMapper with empty string instead of undefined (#14507)
[jest-snapshot] Allow for strings as well as template literals in inline snapshots (#14465)
[@jest/test-sequencer] Calculate test runtime if perStats.duration is missing (#14473)

Performance

[@jest/create-cache-key-function] Cache access of NODE_ENV and BABEL_ENV (#14455)

Chore & Maintenance

[jest-cli] Move internal config initialisation logic to the create-jest package (#14465)

Readme

Source