ts-jest TypeScript Unit Testing Jest Integration Guide 2026
ts-jest is the official TypeScript preprocessor for Jest, transforming .ts and .tsx source files into JavaScript that Jest can execute. With 22.7 million weekly npm downloads in 2026, it remains the standard integration layer for TypeScript projects using Jest. What Is ts-jest and Why It Still Matters in 2026 ts-jest is a TypeScript preprocessor for Jest that compiles .ts and .tsx files at test runtime using the TypeScript compiler (tsc). Unlike Babel-based approaches, ts-jest performs real TypeScript type checking during test execution, giving you full type safety without a separate compilation step. As of 2026, ts-jest v29.4.9 supports Jest 29–30 and TypeScript 5.x, with 22.7 million weekly npm downloads and 7,077+ GitHub stars. The package has 3,729 direct dependents on npm, making it deeply embedded in the JavaScript ecosystem. ...