Jestlike

Jestlike is an open-source JavaScript testing framework designed to mimic Jest’s developer experience while offering its own enhancements. It provides zero-configuration setup for common projects, an integrated assertion API, and a test runner that prioritizes deterministic, fast test execution.

The project was started in 2022 by the open-source collective NovaLabs. The first stable release appeared in 2023, focusing on fast startup, parallel test execution, and snapshot testing. Since then, Jestlike has added TypeScript support, ES module compatibility, and an extensible plugin system.

Features: Core features include built-in snapshot testing, mock functions, code coverage, watch mode, and a concise CLI. It supports TypeScript and both CommonJS and ES modules, with tests running in parallel via worker threads. A plugin API enables custom reporters and test environments.

Architecture and performance: The framework comprises a test runner, assertion layer, snapshot engine, and plugin API. Tests execute in isolated workers to maximize CPU utilization, with a caching layer to accelerate repeated runs. It emphasizes deterministic results through sandboxed environments and stable module resolution.

Reception and impact: Jestlike has a growing, albeit smaller, community compared with Jest. It is adopted by several open-source projects seeking a Jest-like experience with a different plugin model. Compatibility with Jest APIs is generally good for common tests, though some plugins and edge cases may require adjustments.