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jest-matcher-utils
Advanced tools
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
jest 20.0.0
--projects
option to run one instance of Jest in multiple projects at the same time. (#3400)expect
matchers through .resolves
and .rejects
. (#3068)expect.hasAssertions()
function similar to expect.assertions()
. (#3379)this.equals
function exposed to custom matchers. (#3469)valid-expect
lint rule in eslint-plugin-jest
. (#3067)@jest-environment
in the docblock. (#2859)reporters
in the configuration. (#3349)jest-editor-support
into a separate jest-test-typescript-parser
package. (#2973)babel-jest
to look up the babel
field in package.json
as a fallback.jest-editor-support
's parser to not crash on incomplete ASTs. (#3259)jest-resolve
to use is-builtin-module
instead of resolve.isCore
. (#2997)jest-snapshot
to normalize line endings in the serialize
function. (#3002)--silent
flag. (#3003)notify
option not taking precedence over config option. (#3340)jest-editor-support
. (#3344)undefined
. (#3354)expect
. (#3306)expect.assertions
error. (#3033)jest-file-exists
. (#3105)Config
type. (#3366)jest-file-exists
. (#3101)FAQs
A set of utility functions for expect and related packages
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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