jest-snapshot

What is jest-snapshot?

The jest-snapshot package is a part of the Jest testing framework. It allows developers to capture snapshots of values, typically React component trees, and compare them to previously recorded snapshots to detect changes. This is useful for ensuring that UI does not change unexpectedly.

What are jest-snapshot's main functionalities?

Snapshot Testing

This feature allows you to create a snapshot of a value, which will be saved to a file. On subsequent test runs, the saved snapshot is compared to the current value, and any differences will cause the test to fail. This is useful for testing the output of components.

expect(value).toMatchSnapshot();

Inline Snapshots

Inline snapshots work similarly to regular snapshots, but instead of saving the snapshot to a separate file, it is embedded directly in the test file. This can be more convenient for smaller snapshots or when you want to keep the test and its expected output closely tied together.

expect(value).toMatchInlineSnapshot();

Snapshot Property Matchers

Snapshot property matchers allow you to ignore certain properties within a snapshot by using matchers from Jest's expect API. This is useful when you want to ignore dynamic values that change between test runs, such as timestamps or generated IDs.

expect(value).toMatchSnapshot({ createdAt: expect.any(Date) });

Other packages similar to jest-snapshot

chai-jest-snapshot

This package integrates Jest's snapshot testing feature with the Chai assertion library. It allows developers using Chai to utilize snapshot testing in a similar way to Jest. It is useful for those who prefer Chai's syntax but want to leverage snapshot testing.

ava

AVA is a test runner that comes with built-in support for snapshot testing. While it serves a similar purpose to Jest's snapshot feature, AVA is a separate testing framework with its own syntax and features. It is designed to be fast and concurrent.

mocha-snapshots

This package adds snapshot testing capabilities to the Mocha test framework. It allows Mocha users to take advantage of snapshot testing without switching to Jest. However, it may not be as tightly integrated or feature-rich as Jest's built-in snapshot functionality.

README

The README file is missing

Changelog

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)