AVA is a test runner for Node.js that offers a concise API, detailed error output, and support for new language features and process isolation. AVA is best-suited for testing Node.js modules and server applications, but perhaps not for testing UI applications. Among its capabilities, AVA offers a feature to mark a test as a “to do” task. Each test file run is a separate process. Other benefits cited include AVA’s minimalism and speed, simple test syntax, and ability to run tests concurrently. AVA also has support for async functions and observables—an observable being a type that can be used to model push-based data sources such as DOM events.