ts-custom-error

Extending Error does not work completely correctly with TypeScript starting with v2.1.

While there isn't a completely function way of fixing this, this utility seeks at least make unit testing custom errors a little easier. It works by completely replacing the Error object on the global scope. This of course means that using this on your actual build is likely a terrible idea, but it will help you test your custom errors.

Note that this is not required for working with plain ES code, since it works correctly with Node (v8) and most browsers. The problem is specific to TypeScript.

Installation

Install from NPM:

npm install ts-custom-error

Usage

All that is needed for use is to import the package at the beginning of your tests (before your actual code is imported). Since it replaces the Error class, you do not need to change any of your custom errors to subclass anything other than Error.

Mocha:

mocha --require ts-custom-error src/**/*.spec.ts

Others:

import 'ts-custom-error';