Test Runner
In plain terms
A tool that executes tests and reports results.
Going deeper
A test runner discovers, runs, and reports on tests, often with features like parallelism, filtering, and coverage. It orchestrates test execution.
Under the hood
Integrates with CI and IDEs; handles setup, isolation, and result formatting.
Examples
Jest, pytest, JUnit runner, Mocha, Vitest, CI integration.
Think of it like...
Like a proctor administering an exam and tallying the scores.