jestjs/jest · error · ValidationError

Option "${path}.${option}" must be of type: ${validTyp

Error message

  Option "${path}.${option}" must be of type:
    ${validTypes}
  but instead received:
    ${getType(received)}

  Example:
${formatExamples(option, conditions)}

What it means

Thrown by `errorMessage` in jest-validate (errors.ts:24-37, throws as `ValidationError`) when a config option's value fails its type condition. The validator compares the received value's type against the set of types observed across the option's example/default values; on mismatch it prints the expected types, the received type, and a concrete example block.

Source

Thrown at packages/jest-validate/src/errors.ts:37

  path?: Array<string>,
): void => {
  const conditions = getValues(defaultValue);
  const validTypes: Array<string> = [...new Set(conditions.map(getType))];

  const message = `  Option ${chalk.bold(
    `"${path && path.length > 0 ? `${path.join('.')}.` : ''}${option}"`,
  )} must be of type:
    ${validTypes.map(e => chalk.bold.green(e)).join(' or ')}
  but instead received:
    ${chalk.bold.red(getType(received))}

  Example:
${formatExamples(option, conditions)}`;

  const comment = options.comment;
  const name = (options.title && options.title.error) || ERROR;

  throw new ValidationError(name, message, comment);
};

function formatExamples(option: string, examples: Array<unknown>) {
  return examples.map(
    e => `  {
    ${chalk.bold(`"${option}"`)}: ${chalk.bold(formatPrettyObject(e))}
  }`,
  ).join(`

  or

`);
}

View on GitHub (pinned to f49721c78e)

Solutions

1. Read the message's `must be of type` line and the example block - they name the exact shape expected.
2. Open the Jest config docs for the named option and match the documented type.
3. Run Jest with `--showConfig` or `--listTests` to surface validation before running tests.
4. If overriding via env vars (e.g. `--maxWorkers`), ensure CLI/coercion produces the right type.

Example fix

// before
module.exports = { coverageThreshold: { global: 'lines' } }; // 'lines' should be a number
// after
module.exports = { coverageThreshold: { global: { lines: 80 } } };

// Validate config types against the example/default before running Jest
const { validate } = require('jest-validate');
validate(myConfig, { exampleConfig: defaultJestConfig, title: { warn: '', error: 'jest.config.js' } });

const isObjectType = (v: unknown, t: 'object' | 'string' | 'number' | 'boolean' | 'function'): boolean =>
  t === 'object' ? (typeof v === 'object' && v !== null && !Array.isArray(v)) : typeof v === t;

When it happens

Trigger: Setting a Jest config option to a value whose runtime type doesn't match any of the types present in the default/example config: e.g. coverageThreshold set to a string instead of object, testMatch set to a single string instead of an array of strings (testMatch is array-typed), coveragePathIgnorePatterns set to a single string instead of an array.

Common situations: Hand-typed jest.config.js where the shape doesn't match the docs; copy-pasting a single value where Jest wants an array (or vice versa); passing a function where a value is expected; environment-variable overrides coerced to the wrong type.

Related errors

• ${key} has to be of type string or number
• The option summaryThreshold should be a number
• Custom snapshot resolver must implement a `${propName}` as a
• ● Invalid transformer module: "${slash(transformPath)}" sp
• Invalid first argument, ${descriptor}. It must be a named cl

AI-assisted analysis of jestjs/jest@f49721c78e (2026-08-03). Data as JSON: /data/errors/b1d1e8c6b775c894.json. Report an issue: GitHub.