https://github.com/vstirbu/chai-as-typed

Chai assertions for types defined via JSDoc
https://github.com/vstirbu/chai-as-typed

chai jsdoc testing types typescript

Last synced: 20 days ago
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Chai assertions for types defined via JSDoc

• Host: GitHub
• URL: https://github.com/vstirbu/chai-as-typed
• Owner: vstirbu
• License: mit
• Created: 2017-10-24T11:50:20.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2021-08-02T03:15:23.000Z (over 3 years ago)
• Last Synced: 2025-01-03T20:18:17.775Z (29 days ago)
• Topics: chai, jsdoc, testing, types, typescript
• Language: JavaScript
• Homepage:
• Size: 2.07 MB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 5
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# chai-as-typed

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## Motivation

[TypeScript](https://www.typescriptlang.org/) has now the ability to do [type checking](https://github.com/Microsoft/TypeScript/wiki/Type-Checking-JavaScript-Files) in plain JavaScript files. This behavior is not based on magic, but on well formed JSDoc [comments](https://github.com/Microsoft/TypeScript/wiki/JSDoc-support-in-JavaScript).

Now, if I have a JavaScript file augmented with the proper JSDoc comments, an editor such as [Visual Studio Code]() will be able to automatically get IntelliSense, which includes autocompletion and type checking:

![](https://raw.github.com/vstirbu/chai-as-typed/master/media/fsm-events-typescript.gif)

However, exposing reliably the type information about a module APIs requires testing. This plugin enhances Chai with specific helpers that make the task of checking the type information in plain JavaScript files easy.

## How to use

Considering that we have a javascript file, which starts with the following line:

```javascript

// @ts-check

```

we can test that the types used are correct with the following assertion:

```javascript

expect('/absolute/path/to/filename.js').to.have.types.validated();

```

If there are type errors, an error will be thrown indicating the position of the type violations:

```

Error: /absolute/path/to/filename.js (Ln 5, Col 6): Argument of type '123' is not assignable to parameter of type 'string'

```

Also, in case errors are expected, we can test using the following assertions indicating the number of errors expected:

```javascript

expect('/absolute/path/to/filename.js').to.have.types.errors(1);

```

## Installation ans setup

Do `npm install --save-dev chai-as-typed`, then:

```javascript

var chai = require('chai');

var chaiAsTyped = require('chai-as-typed');

chai.use(chaiAsTyped);

```

## Disclaimer

The plugin is in experimental phase. Use it gently and provide feedback! :)