Jest

Jest discovers and runs test files with a zero-config setup for Node.js and React projects. It provides expect assertions, mock functions, module mocking, and snapshot comparisons, with parallel test execution and Istanbul-based coverage reports.

Codeaxes uses Jest as the default unit test runner for TypeScript, React, NestJS, and Node.js codebases because it integrates with minimal configuration and covers mocking patterns needed for isolated service and component tests.