expect-rejection

A tiny library meant to scratch a personal itch.

If you want to test promise rejections in Chai, you can, but you need boilerplate. This package provides the boilerplate.

Background

I've gradually been phasing chai-as-promised out of my test suites. I used it a lot and even contributed substantial code to it but the use of async/await has lessened the need for it, and the direction chai-as-promised has been taking lately is not to my liking. At this point, the only thing that chai-as-promised can concisely do that Chai and async/await cannot is test rejections.

So I've been using boilerplate to test rejections in this test suite, and that test suite, and that other suite, etc. I'm tired of the code duplication. Hence this library.

Usage

Version 2 requires that you FIRST use the use function exported by this library to link this library with Chai.

Then you can call expectRejection. Read the TypeScript code for detailed documentation about parameters, etc.

import * as chai from "chai";
import { expectRejection, use } from "expect-rejection";

use(chai);

expectRejection(...);

FAQ

Q. Why [...] ?

A. An overarching answer to just about any "why..." question is "because this library is meant to scratch a personal itch." Many of my libraries are aiming to reach a wider audience, but not this one.

Q. Why TypeScript? Isn't this too small a library to bother with TS?

A. I'm using TS a lot. So I want a TS definition files but I don't like maintaining such files manually. So, yeah the source is in TS and I automatically get definition files from it. You can still use the library with plain JS if you want.

Q. Why not a Chai plugin?

A. I cannot be bothered. I've had the experience of dealing with the intricacies of Chai plugins. I'd rather not revisit. If you want to create a Chai plugin from this code, have at it.