`assert-exception` is a tiny utility library that simplifies testing for thrown errors and rejected promises. It provides two helper functions—`throws(fn)` that runs a function and returns the thrown `Error` (or an empty object if nothing is thrown), and `rejects(promise)` that resolves with the rejection reason—making assertions in test suites more concise. The package is aimed at JavaScript developers who write unit tests (especially with assertion libraries like power‑assert) and want a cleaner syntax for exception‑related checks.