Nock‑exec is a lightweight Node.js library that lets you mock calls to `child_process.exec` in tests, using a syntax similar to the popular HTTP‑mocking tool Nock. By defining expected command strings, optional errors, exit codes, and output, developers can reliably simulate command‑line execution without spawning real processes, making unit‑testing of code that relies on `exec` faster and deterministic. It’s aimed at Node developers who need to stub out external CLI commands during automated testing.