Ceylon is an assertion library for unit testing written in TypeScript. It can be used in TypeScript or in plain old JavaScript.
It is based upon the API for expect, with the added bonus of full TypeScript definitions, meaning there's no need to go looking for a d.ts file.
Ceylon aims to simplify unit testing in TypeScript by making it easy to write assertions.
import expect from 'ceylon';
expect(100)
.toExist()
.toBeA('number')
.toBeLessThan(200)
.toBeGreaterThan(5)
.toNotBe(90);
For a complete reference visit the Ceylon Wiki.