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Generic configuration validation tool that helps you with warnings, errors and deprecation messages as well as showing users examples of correct configuration.

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Package description

What is jest-validate?

The jest-validate package is a utility for validating and ensuring that configurations passed to Jest, the JavaScript testing framework, are correct. It checks if the provided configuration object adheres to Jest's expected configurations and provides warnings or errors for any invalid or unknown options. This helps developers to quickly identify issues with their Jest setup.

What are jest-validate's main functionalities?

Validation of configuration objects

This feature allows developers to validate their Jest configuration objects against a schema. It ensures that the configuration provided matches the expected format and values that Jest can work with.

{"validateConfig": require('jest-validate').validateConfig, "config": { "verbose": true }, "exampleConfig": { "verbose": false }}

Customization of validation messages

Developers can provide custom messages for unknown or deprecated options. This helps in guiding the user to correct their configuration with helpful feedback.

{"validateConfig": require('jest-validate').validateConfig, "config": { "unknownOption": true }, "exampleConfig": { "verbose": false }, "options": { "comment": "A custom message for unknownOption" }}

Deprecation warnings

jest-validate can warn users about deprecated configuration options. It provides a mechanism to inform users about the new options they should use instead.

{"validateConfig": require('jest-validate').validateConfig, "config": { "scriptPreprocessor": "<rootDir>/preprocessor.js" }, "exampleConfig": { "transform": {"^.+\\.js$": "<rootDir>/preprocessor.js"} }, "deprecatedConfig": { "scriptPreprocessor": "Please use `transform` instead" }}

Other packages similar to jest-validate





  • [create-jest] Add npm init / yarn create initialiser for Jest projects (#14465)
  • [jest-validate] Allow deprecation warnings for unknown options (#14499)


  • [jest-resolver] Replace unmatched capture groups in moduleNameMapper with empty string instead of undefined (#14507)
  • [jest-snapshot] Allow for strings as well as template literals in inline snapshots (#14465)
  • [@jest/test-sequencer] Calculate test runtime if perStats.duration is missing (#14473)


  • [@jest/create-cache-key-function] Cache access of NODE_ENV and BABEL_ENV (#14455)

Chore & Maintenance

  • [jest-cli] Move internal config initialisation logic to the create-jest package (#14465)




Generic configuration validation tool that helps you with warnings, errors and deprecation messages as well as showing users examples of correct configuration.

npm install --save jest-validate


import {validate} from 'jest-validate';

validate(config, validationOptions); // => {hasDeprecationWarnings: boolean, isValid: boolean}

Where ValidationOptions are:

type ValidationOptions = {
  comment?: string;
  condition?: (option: unknown, validOption: unknown) => boolean;
  deprecate?: (
    config: Record<string, unknown>,
    option: string,
    deprecatedOptions: DeprecatedOptions,
    options: ValidationOptions,
  ) => boolean;
  deprecatedConfig?: DeprecatedOptions;
  error?: (
    option: string,
    received: unknown,
    defaultValue: unknown,
    options: ValidationOptions,
    path?: Array<string>,
  ) => void;
  exampleConfig: Record<string, unknown>;
  recursive?: boolean;
  recursiveBlacklist?: Array<string>;
  recursiveDenylist?: Array<string>;
  title?: Title;
  unknown?: (
    config: Record<string, unknown>,
    exampleConfig: Record<string, unknown>,
    option: string,
    options: ValidationOptions,
    path?: Array<string>,
  ) => void;

type Title = {
  deprecation?: string;
  error?: string;
  warning?: string;

exampleConfig is the only option required.


By default jest-validate will print generic warning and error messages. You can however customize this behavior by providing options: ValidationOptions object as a second argument:

Almost anything can be overwritten to suite your needs.


  • recursiveDenylist – optional array of string keyPaths that should be excluded from deep (recursive) validation.
  • comment – optional string to be rendered below error/warning message.
  • condition – an optional function with validation condition.
  • deprecate, error, unknown – optional functions responsible for displaying warning and error messages.
  • deprecatedConfig – optional object with deprecated config keys.
  • exampleConfig – the only required option with configuration against which you'd like to test.
  • recursive - optional boolean determining whether recursively compare exampleConfig to config (default: true).
  • title – optional object of titles for errors and messages.

You will find examples of condition, deprecate, error, unknown, and deprecatedConfig inside source of this repository, named respectively.

exampleConfig syntax

exampleConfig should be an object with key/value pairs that contain an example of a valid value for each key. A configuration value is considered valid when:

  • it matches the JavaScript type of the example value, e.g. string, number, array, boolean, function, or object
  • it is null or undefined
  • it matches the Javascript type of any of arguments passed to MultipleValidOptions(...)

The last condition is a special syntax that allows validating where more than one type is permissible; see example below. It's acceptable to have multiple values of the same type in the example, so you can also use this syntax to provide more than one example. When a validation failure occurs, the error message will show all other values in the array as examples.


Minimal example:

validate(config, {exampleConfig});

Example with slight modifications:

validate(config, {
  comment: '  Documentation:',
  title: {
    deprecation: 'Custom Deprecation',
    // leaving 'error' and 'warning' as default

This will output:

● Validation Warning:

  Unknown option transformx with value "<rootDir>/node_modules/babel-jest" was found.
  This is either a typing error or a user mistake. Fixing it will remove this message.

● Validation Error:

  Option transform must be of type:
  but instead received:

    "transform": {
      "\\.js$": "<rootDir>/preprocessor.js"


Example validating multiple types

import {multipleValidOptions} from 'jest-validate';

validate(config, {
  // `bar` will accept either a string or a number
  bar: multipleValidOptions('string is ok', 2),
● Validation Error:

  Option foo must be of type:
    string or number
  but instead received:

    "bar": "string is ok"


    "bar": 2


Based on deprecatedConfig object with proper deprecation messages. Note custom title:

Custom Deprecation:

  Option scriptPreprocessor was replaced by transform, which support multiple preprocessors.

  Jest now treats your current configuration as:
    "transform": {".*": "xxx"}

  Please update your configuration.


Example validating CLI arguments

import {validate} from 'jest-validate';

validateCLIOptions(argv, {...allowedOptions, deprecatedOptions});

If argv contains a deprecated option that is not specifid in allowedOptions, validateCLIOptions will throw an error with the message specified in the deprecatedOptions config:

● collectCoverageOnlyFrom:

  Option "collectCoverageOnlyFrom" was replaced by "collectCoverageFrom"

  CLI Options Documentation:

If the deprecation option is still listed in the allowedOptions config, then validateCLIOptions will print the warning wihout throwing an error.


Last updated on 12 Sep 2023

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