Jest and Vitest are two well-known JavaScript testing frameworks, each with its own strengths. Jest, created by Facebook, is especially popular for React applications. It provides a "zero-config" setup, built-in code coverage reporting, and snapshot testing, making it a complete solution for many JavaScript projects. Vitest, a newer framework in the Vite ecosystem, is known for its speed and lightweight design. Using Vite’s dev server, Vitest performs very well, especially in larger projects.