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
28.1.1
[jest] Expose Config type (#12848)[@jest/reporters] Improve GitHubActionsReporters annotation format (#12826)[@jest/types] Infer argument types passed to test and describe callback functions from each tables (#12885, #12905)[@jest/expect-utils] Fix deep equality of ImmutableJS OrderedMaps (#12899)[jest-docblock] Handle multiline comments in parseWithComments (#12845)[jest-mock] Improve spyOn error messages (#12901)[jest-runtime] Correctly report V8 coverage with resetModules: true (#12912)[jest-worker] Make JestWorkerFarm helper type to include methods of worker module that take more than one argument (#12839)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 28,162,754 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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