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jest-matcher-utils
Advanced tools
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.
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-utils
yarn add jest-matcher-utils
stringify
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
29.4.0
[expect, @jest/expect-utils]
Support custom equality testers (#13654)[jest-config, jest-worker]
Use os.availableParallelism
if available to calculate number of workers to spawn (#13738)[@jest/globals, jest-mock]
Add jest.replaceProperty()
that replaces property value (#13496)[jest-haste-map]
ignore Sapling vcs directories (.sl/
) (#13674)[jest-resolve]
Support subpath imports (#13705, #13723, #13777)[jest-runtime]
Add jest.isolateModulesAsync
for scoped module initialization of asynchronous functions (#13680)[jest-runtime]
Add jest.isEnvironmentTornDown
function (#13741)[jest-test-result]
Added skipped
and focused
status to FormattedTestResult
(#13700)[jest-transform]
Support for asynchronous createTransformer
(#13762)[jest-environment-node]
Fix non-configurable globals (#13687)[@jest/expect-utils]
toMatchObject
should handle Symbol
properties (#13639)[jest-mock]
Fix mockReset
and resetAllMocks
undefined
return value(#13692)[jest-resolve]
Add global paths to require.resolve.paths
(#13633)[jest-resolve]
Correct node core module detection when using node:
specifiers (#13806)[jest-runtime]
Support WASM files that import JS resources (#13608)[jest-runtime]
Use the scriptTransformer
cache in jest-runner
(#13735)[jest-runtime]
Enforce import assertions when importing JSON in ESM (#12755 & #13805)[jest-snapshot]
Make sure to import babel
outside of the sandbox (#13694)[jest-transform]
Ensure the correct configuration is passed to preprocessors specified multiple times in the transform
option (#13770)FAQs
A set of utility functions for expect and related packages
The npm package jest-matcher-utils receives a total of 27,961,950 weekly downloads. As such, jest-matcher-utils popularity was classified as popular.
We found that jest-matcher-utils demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 6 open source maintainers collaborating on the project.
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