jest-matcher-utils
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Package description
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.
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)}`);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 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.
Changelog
29.6.0
[jest-circus, jest-snapshot] Add support for snapshot matchers in concurrent tests (#14139)[jest-cli] Include type definitions to generated config files (#14078)[jest-snapshot] Support arrays as property matchers (#14025)[jest-core, jest-circus, jest-reporter, jest-runner] Added support for reporting about start individual test cases using jest-circus (#14174)[jest-circus] Prevent false test failures caused by promise rejections handled asynchronously (#14110)[jest-config] Handle frozen config object (#14054)[jest-config] Allow coverageDirectory and collectCoverageFrom in project config (#14180)[jest-core] Always use workers in watch mode to avoid crashes (#14059).[jest-environment-jsdom, jest-environment-node] Fix assignment of customExportConditions via testEnvironmentOptions when custom env subclass defines a default value (#13989)[jest-matcher-utils] Fix copying value of inherited getters (#14007)[jest-mock] Tweak typings to allow jest.replaceProperty() replace methods (#14008)[jest-mock] Improve user input validation and error messages of spyOn and replaceProperty methods (#14087)[jest-runtime] Bind jest.isolateModulesAsync to this (#14083)[jest-runtime] Forward wrapperLength to the Script constructor as columnOffset for accurate debugging (#14148)[jest-runtime] Guard _isMockFunction access with in (#14188)[jest-snapshot] Fix a potential bug when not using prettier and improve performance (#14036)[@jest/transform] Do not instrument .json modules (#14048)[jest-worker] Restart a shut down worker before sending it a task (#14015)[*] Update semver dependency to get vulnerability fix (#14262)[docs] Updated documentation for the --runTestsByPath CLI command (#14004)[docs] Updated documentation regarding the synchronous fallback when asynchronous code transforms are unavailable (#14056)[docs] Update jest statistics of use and downloads in website Index.Readme
This package's exports are most notably used by expect's this.utils.
To add this package as a dependency of a project, run either of the following commands:
npm install jest-matcher-utilsyarn add jest-matcher-utilsstringify highlightTrailingWhitespace printReceived printExpected printWithType ensureNoExpected ensureActualIsNumber ensureExpectedIsNumber ensureNumbers ensureExpectedIsNonNegativeInteger printDiffOrStringify diff pluralize getLabelPrinter matcherErrorMessage matcherHint
MatcherHintOptions DiffOptions
EXPECTED_COLOR RECEIVED_COLOR INVERTED_COLOR BOLD_WEIGHT DIM_COLOR SUGGEST_TO_CONTAIN_EQUAL
FAQs
A set of utility functions for expect and related packages
The npm package jest-matcher-utils receives a total of 33,055,172 weekly downloads. As such, jest-matcher-utils popularity was classified as popular.
We found that jest-matcher-utils demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 6 open source maintainers collaborating on the project.
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