testdouble.js

testdouble.js (AKA td.js) is an opinionated, minimalist test double library for JavaScript and TypeScript, designed to facilitate test-driven development (TDD). It provides robust mechanisms for creating mocks, stubs, and spies to replace real dependencies within tests, promoting terse, clear, and easy-to-understand test suites. As of version 3.20.2, the library is actively maintained by Test Double, a software agency. It maintains a steady release cadence for bug fixes and minor features within its major versions. The library is framework-agnostic, compatible with popular test runners like Jest, Mocha, and Jasmine, and functions reliably in both Node.js and browser environments. Its primary differentiator is its strong opinions on TDD practices, aiming to guide developers toward healthier mocking patterns rather than simply offering a comprehensive feature set without guidance.