jest-matcher-utils

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)}`);