ts-jest

library29.4.9jsnpmunverified

ts-jest is a Jest transformer with source map support that enables testing projects written in TypeScript using Jest. It supports all TypeScript features, including type-checking. The current stable version is 29.4.9. Note that ts-jest does not follow semantic versioning, which means major breaking changes can occur without a corresponding major version increment. Releases are frequent, primarily for patch updates.

testing

npm install ts-jest

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · TS-JEST

ts-jest

testingjavascriptv29.4.9

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

This quickstart shows how to set up `ts-jest` for a basic TypeScript project. It includes the necessary `package.json` dependencies and `scripts`, a minimal `jest.config.ts` (generated via `npx ts-jest config:init`), a simple TypeScript function, and its corresponding test file. After installation and configuration, tests can be run using `npm test`.

{ "devDependencies": { "jest": "^29.4.9", "typescript": "^5.0.0", "ts-jest": "^29.4.9", "@types/jest": "^29.4.9" }, "scripts": { "test": "jest" } } // jest.config.ts (created by `npx ts-jest config:init`) export default { preset: 'ts-jest', testEnvironment: 'node', roots: ['<rootDir>/src'], }; // src/sum.ts export function sum(a: number, b: number): number { return a + b; } // src/sum.test.ts import { sum } from './sum'; describe('sum', () => { it('adds two numbers', () => { expect(sum(1, 2)).toBe(3); }); });

Debug

Known issues

breakingts-jest explicitly states it does not follow semantic versioning. This means breaking changes can occur in minor or even patch releases, making upgrades potentially risky.

fix

Always review the CHANGELOG.md before upgrading ts-jest, especially across minor versions, and thoroughly test your application after any update.

affects: >=23.10.0

gotchats-jest has strict peer dependency requirements for Jest and TypeScript versions. Incompatible versions can lead to unexpected errors or installation failures.

fix

Ensure that your installed versions of `jest` (`^29.0.0 || ^30.0.0`) and `typescript` (`>=4.3 <7`) match the peer dependency range specified by ts-jest.

affects: >=29.0.0

gotchaThere's a fundamental difference between using `ts-jest` for TypeScript compilation and using Babel with `@babel/preset-typescript`. `ts-jest` handles type-checking and Jest integration, while Babel with `preset-typescript` only strips types, potentially missing type errors.

fix

Choose the appropriate tool based on your project's needs. If you require full TypeScript type-checking during tests, `ts-jest` is the correct choice. If you only need fast transpilation without type checks, Babel might be preferred (though often used with other transformers).

affects: *

Errors

Common errors & fixes

Jest: ts-jest preset was not applied. Ensure that you have configured jest.config.js/ts to use a preset.

The Jest configuration file (`jest.config.js` or `jest.config.ts`) does not include `preset: 'ts-jest'`.

fix

Add `preset: 'ts-jest'` to your Jest configuration file, for example: `export default { preset: 'ts-jest' };`

Cannot find module 'typescript' or 'jest' or '@jest/types'

A required peer dependency of `ts-jest` (like `typescript`, `jest`, `@jest/types`, `babel-jest`, etc.) is not installed or its version is incompatible.

fix

Install all necessary peer dependencies explicitly using `npm install -D jest typescript @types/jest ts-jest` (or `yarn add --dev ...`) and ensure their versions fall within the ranges specified by `ts-jest`.

Error: Jest: a transformer must at least provide a `process` function.

This usually indicates an incompatibility between `ts-jest` and the installed version of Jest or TypeScript, or a corrupted `node_modules`.

fix

Verify that your `jest` and `typescript` versions satisfy `ts-jest`'s peer dependency requirements. Try clearing your `node_modules` and `npm cache clean --force` (or `yarn cache clean`), then reinstall dependencies.

TSxxxx: [TypeScript compilation error]

TypeScript compiler errors are being reported during the test run, indicating issues with your code's types or `tsconfig.json` configuration.

fix

Address the specific TypeScript errors in your source or test files. Ensure your `tsconfig.json` (especially `compilerOptions` like `target`, `module`, `strict`) is correctly configured for your project and `ts-jest`.

Upgrade

Version history

29.4.9latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

11 hits · last 30 days

node

Resources

githubhttps://github.com/kulshekhar/ts-jest ↗

packagehttps://www.npmjs.com/package/ts-jest ↗

homepagehttps://kulshekhar.github.io/ts-jest ↗