ts-jest is a Jest transformer that lets you use Jest to test projects written in TypeScript.
The tool solves the problem of running TypeScript code through Jest, which natively expects JavaScript. It works by acting as a transformer in Jest's pipeline, converting TypeScript to JavaScript on the fly while preserving source maps so that stack traces and debugging information point back to the original TypeScript source. The transformer supports all TypeScript features including type-checking, distinguishing it from approaches like Babel with preset-typescript.
Teams should choose ts-jest if they are testing TypeScript projects and want tight integration with Jest without additional build steps. It suits projects already committed to Jest as their test runner. The tool requires TypeScript and Jest as prerequisites and provides a configuration initialization command to set up the necessary Jest configuration automatically.
The project maintains active engagement with its community through multiple channels including Discord and GitHub Discussions, and explicitly seeks collaborators to help improve the codebase. The tool underwent a significant rewrite at a major version boundary, which represents a substantial evolution in its architecture and approach.
