typesjest

Typesjest is a term used to describe the integration of TypeScript type definitions with the Jest testing framework to enable type-safe test code. It is not a separate software project; rather, it refers to using TypeScript’s type system to validate Jest’s API and related testing utilities.

The most common source of these typings is the DefinitelyTyped repository, published under the package @types/jest. These definitions provide typings for Jest’s global functions (describe, it, test, expect), setup and teardown hooks (beforeEach, afterAll, etc.), and typing for mocks, spies, and various matchers. They also include type definitions for commonly used Jest features such as mocking modules and timers, as well as TypeScript support for custom Jest environments.

Usage typically involves installing the type definitions in a TypeScript-enabled Jest project: npm install --save-dev @types/jest. In many setups the typings are picked up automatically, but sometimes you need to configure tsconfig.json to include "types": ["jest"] or to ensure the module resolution sees the typings. For projects using ts-jest or Babel-based transpilation, the typings complement runtime configuration by providing compile-time safety without affecting runtime behavior.

Limitations include that typings are maintained by the community and may lag behind new Jest releases; some advanced Jest APIs may require additional typings or manual augmentation. It is advisable to align the @types/jest version with the Jest version in use and to consult the DefinitelyTyped repository for compatibility notes.