Tinyspy is a tiny, yet powerful, mocking and spying library for JavaScript. It offers essential features like spyOn, fn, and assertions such as toHaveBeenCalled without the bloat of larger testing frameworks. This lightweight package is perfect for focused unit testing, providing fine-grained control over function behavior and observation. Its minimal footprint makes it ideal for resource-constrained environments and projects prioritizing speed and simplicity. Use it to isolate components and ensure their reliable interaction.