https://github.com/lionralfs/assert.macro

A babel macro to add assertions for development/testing purposes
https://github.com/lionralfs/assert.macro

assert assertions babel-macro babel-plugin-macros javascript macro

Last synced: 3 days ago
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A babel macro to add assertions for development/testing purposes

• Host: GitHub
• URL: https://github.com/lionralfs/assert.macro
• Owner: lionralfs
• License: mit
• Created: 2019-05-12T00:01:21.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2023-02-03T11:46:25.000Z (almost 2 years ago)
• Last Synced: 2025-01-15T08:29:06.568Z (15 days ago)
• Topics: assert, assertions, babel-macro, babel-plugin-macros, javascript, macro
• Language: JavaScript
• Homepage:
• Size: 1.97 MB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# assert.macro [![Babel Macro](https://img.shields.io/badge/babel--macro-%F0%9F%8E%A3-f5da55.svg)](https://github.com/kentcdodds/babel-plugin-macros)

A babel macro to add assertions for development/testing purposes.



[![Build Status](https://travis-ci.com/lionralfs/assert.macro.svg?branch=master)](https://travis-ci.com/lionralfs/assert.macro)

## Installation

This project relies on [babel-plugin-macros](https://github.com/kentcdodds/babel-plugin-macros), you can install both from npm:

```sh

npm install --save-dev assert.macro babel-plugin-macros

```

#### Babel config

In your babel config, add `"macros"` to your plugins:

```json

{

  "plugins": ["macros"]

}

```

#### Enabling the assertions

To include the assertions in the babel output, make sure you set the `ENABLE_ASSERTIONS` environment variable to `"true"`. For example:

```sh

ENABLE_ASSERTIONS=true npm run build

```

All usages of of the call to `assert`, including the import will be removed completely, if `ENABLE_ASSERTIONS` is **not** `"true"`.

## Usage

```js

import assert from 'assert.macro';

class ShoppingCart {

  applyDiscount(discount) {

    assert(discount > 0, "Discount can't be 0 or negative.");

    assert(discount <= 1, "The discount shouldn't make it more expensive.");

    this._total *= discount;

  }

}

```

## Why

- Documents intent

- More explicit than comments

- Able to catch bugs

## Inspirations

- [Refactoring](https://martinfowler.com/books/refactoring.html) by Martin Fowler

- [Programming With Assertions](https://docs.oracle.com/javase/8/docs/technotes/guides/language/assert.html) (Java)

- [Invariant](https://github.com/zertosh/invariant) by Facebook

## License

[MIT](LICENSE) © Lion Ralfs