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

24.9.0

Features

[expect] Highlight substring differences when matcher fails, part 1 (#8448)
[expect] Highlight substring differences when matcher fails, part 2 (#8528)
[expect] Improve report when mock-spy matcher fails, part 1 (#8640)
[expect] Improve report when mock-spy matcher fails, part 2 (#8649)
[expect] Improve report when mock-spy matcher fails, part 3 (#8697)
[expect] Improve report when mock-spy matcher fails, part 4 (#8710)
[expect] Throw matcher error when received cannot be jasmine spy (#8747)
[expect] Improve report when negative CalledWith assertion fails (#8755)
[expect] Improve report when positive CalledWith assertion fails (#8771)
[expect] Display equal values for ReturnedWith similar to CalledWith (#8791)
[expect, jest-snapshot] Change color from green for some args in matcher hints (#8812)
[jest-snapshot] Highlight substring differences when matcher fails, part 3 (#8569)
[jest-core] Improve report when snapshots are obsolete (#8665)
[jest-cli] Improve chai support (with detailed output, to match jest exceptions) (#8454)
[*] Manage the global timeout with --testTimeout command line argument. (#8456)
[pretty-format] Render custom displayName of memoized components (#8546)
[jest-validate] Allow maxWorkers as part of the jest.config.js (#8565)
[jest-runtime] Allow passing configuration objects to transformers (#7288)
[@jest/core, @jest/test-sequencer] Support async sort in custom testSequencer (#8642)
[jest-runtime, @jest/fake-timers] Add jest.advanceTimersToNextTimer (#8713)
[@jest-transform] Extract transforming require logic within jest-core into @jest-transform (#8756)
[jest-matcher-utils] Add color options to matcherHint (#8795)
[jest-circus/jest-jasmine2] Give clearer output for Node assert errors (#8792)
[jest-runner] Export all types in the type signature of jest-runner (#8825)

Fixes

[jest-cli] Detect side-effect only imports when running --onlyChanged or --changedSince (#8670)
[jest-cli] Allow --maxWorkers to work with % input again (#8565)
[babel-plugin-jest-hoist] Expand list of whitelisted globals in global mocks (#8429)
[jest-core] Make watch plugin initialization errors look nice (#8422)
[jest-snapshot] Prevent inline snapshots from drifting when inline snapshots are updated (#8492)
[jest-haste-map] Don't throw on missing mapper in Node crawler (#8558)
[jest-core] Fix incorrect passWithNoTests warning (#8595)
[jest-snapshots] Fix test retries that contain snapshots (#8629)
[jest-mock] Fix incorrect assignments when restoring mocks in instances where they originally didn't exist (#8631)
[expect] Fix stack overflow when matching objects with circular references (#8687)
[jest-haste-map] Workaround a node >=12.5.0 bug that causes the process not to exit after tests have completed and cancerous memory growth (#8787)

Chore & Maintenance

[docs] Replace FlowType with TypeScript in CONTRIBUTING.MD code conventions
[jest-leak-detector] remove code repeat (#8438)
[docs] Add example to jest.requireActual (#8482)
[docs] Add example to jest.mock for mocking ES6 modules with the factory parameter (#8550)
[docs] Add information about using jest.doMock with ES6 imports (#8573)
[docs] Fix variable name in custom-matcher-api code example (#8582)
[docs] Fix example used in custom environment docs (#8617)
[docs] Updated react tutorial to refer to new package of react-testing-library (@testing-library/react) (#8753)
[docs] Updated imports of react-testing-library to @testing-library/react in website (#8757)
[jest-core] Add getVersion (moved from jest-cli) (#8706)
[docs] Fix MockFunctions example that was using toContain instead of toContainEqual (#8765)
[*] Make sure copyright header comment includes license (#8783)
[*] Check copyright and license as one joined substring (#8815)
[docs] Fix WatchPlugins jestHooks.shouldRunTestSuite example that receives an object (#8784)
[*] Enforce LF line endings (#8809)
[pretty-format] Delete obsolete link and simplify structure in README (#8824)
[docs] Fix broken transform link on webpack page (#9155)

Performance

[jest-watcher] Minor optimization for JestHook (#8746)
[@jest/reporters] Prevent runaway CPU usage with --notify on macOS (#8831)

FAQs

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Package last updated on 16 Aug 2019

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