jest-matcher-utils

What is jest-matcher-utils?

The jest-matcher-utils package provides utility functions for creating custom Jest matchers. It is designed to help developers write their own matchers that integrate seamlessly with Jest's built-in expectation system, offering a way to extend Jest's assertion capabilities with custom logic. The utilities provided by this package include formatting values for error messages, comparing values, and generating matcher error messages.

What are jest-matcher-utils's main functionalities?

pretty-format

Formats any JavaScript value for pretty printing, which is useful for generating readable error messages in custom matchers.

const { prettyFormat } = require('jest-matcher-utils');
console.log(prettyFormat({ foo: 'bar' }));

matcherHint

Generates a hint string for a matcher, which can be used at the beginning of error messages to indicate which matcher failed.

const { matcherHint } = require('jest-matcher-utils');
console.log(matcherHint('.toBe'));

printExpected and printReceived

These functions format the expected and received values to be included in error messages, applying color highlighting to improve readability.

const { printExpected, printReceived } = require('jest-matcher-utils');
console.log(`Expected: ${printExpected(true)}
Received: ${printReceived(false)}`);

Other packages similar to jest-matcher-utils

chai

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework. It offers similar functionality to jest-matcher-utils in the sense that it provides a rich set of assertions and plugins to extend its capabilities. However, Chai is a standalone assertion library, not tied to any specific test runner like Jest.

expect

Expect is a minimalist assertion library that comes with Jest but can also be used independently. It provides a similar API for writing test assertions as jest-matcher-utils, but jest-matcher-utils focuses more on the utilities for creating custom matchers rather than providing a comprehensive set of built-in matchers.

README

The README file is missing

Changelog

24.6.0

Features

• [expect]: Improve report when matcher fails, part 13 (#8077)
• [@jest/core] Filter API pre-filter setup hook (#8142)
• [jest-snapshot] Improve report when matcher fails, part 14 (#8132)
• [@jest/reporter] Display todo and skip test descriptions when verbose is true (#8038)
• [jest-runner] Support default exports for test environments (#8163)
• [pretty-format] Support React.Suspense (#8180)
• [jest-snapshot] Indent inline snapshots (#8198)
• [jest-config] Support colors in displayName configuration (#8025)

Fixes

• [jest-circus] Fix test retries with beforeAll/beforeEach failures (#8227)
• [expect] Fix circular references in iterable equality (#8160)
• [jest-changed-files] Change method of obtaining git root (#8052)
• [jest-each] Fix test function type (#8145)
• [jest-fake-timers] getTimerCount not taking immediates and ticks into account (#8139)
• [jest-runtime] Allow json file as manual mock (#8159)
• [pretty-format] Print BigInt as a readable number instead of {} (#8138)
• [jest-core] Fix ability to transform dependencies required from globalSetup script (#8143)
• [@jest/reporters] Fix Cannot read property converageData of null (#8168)
• [jest-worker] JEST_WORKER_ID starts at 1 (#8205)
• [jest-config] Use default cwd even if config contains a cwd property (#7923)
• [jest-resolve-dependencies]: Remove internal peer dependencies (#8215)
• [jest-resolve]: Remove internal peer dependencies (#8215)
• [jest-snapshot]: Remove internal peer dependencies (#8215)
• [jest-resolve] Fix requireActual with moduleNameMapper (#8210)
• [jest-haste-map] Fix haste map duplicate detection in watch mode (#8237)

Chore & Maintenance

• [*] Remove flow from code base (#8061)
• [*] Use property initializer syntax in Jest codebase (#8117)
• [*] Move @types/node to the root package.json (#8129)
• [*] Add documentation and tests related to auto-mocking (#8099)
• [*] Add jest-watch-typeahead as a devDependency (#6449)
• [*] upgrade TS to 3.4.0-dev* for incremental builds (#8149)
• [docs] Improve description of optional arguments in ExpectAPI.md (#8126)

Performance

• [jest-haste-map] Optimize haste map data structure for serialization/deserialization (#8171)
• [jest-haste-map] Avoid persisting haste map or processing files when not changed (#8153)
• [jest-core] Improve performance of SearchSource.findMatchingTests by 15% (#8184)
• [jest-resolve] Optimize internal cache lookup performance (#8183)
• [jest-core] Dramatically improve watch mode performance (#8201)
• [jest-transform] Cache regular expression instead of creating anew for every file in ScriptTransformer (#8235)
• [jest-core] Fix memory leak of source map info and minor performance improvements (#8234)
• [jest-console] Fix memory leak by releasing console output reference when printed to stdout (#8233)
• [jest-runtime] Use Map instead of Object for module registry (#8232)