https://github.com/craigtaub/global-leaks-finder

Manage your tests side-effects
https://github.com/craigtaub/global-leaks-finder

globals mocha mocha-tests node-js nodejs side-effects

Last synced: 2 days ago
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Manage your tests side-effects

• Host: GitHub
• URL: https://github.com/craigtaub/global-leaks-finder
• Owner: craigtaub
• Created: 2017-03-02T21:41:18.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-03-02T22:15:40.000Z (almost 8 years ago)
• Last Synced: 2025-01-14T08:06:08.787Z (11 days ago)
• Topics: globals, mocha, mocha-tests, node-js, nodejs, side-effects
• Language: JavaScript
• Size: 5.86 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Global Leaks finder

A mocha-based testing tool to help find tests which are leaking globals.

The aim is to help catch and avoid tests with unexpected side-effects.

It does add significant time to the job so best run only occasionally. See below for explanation how it works.

## Why?

Take this example. Before each test the `browser` is set and after it is reset. *However* we do not know what the value was before this unit test ran or if `false` is a reliable value for later tests. This is an example of a global leakage and is easily missed.

```js

beforeEach(() => {

  process.browser = true;

});

afterEach(() => {

  process.browser = false; // BAD

});

```

Running the tool on this test would throw an error to the console `Error: Global has changed` on the test spec which has leaked, allowing you to catch and manage the problem.

The test has now been improved.

```js

let cached;

beforeEach(() => {

  cached = process.browser;

  process.browser = true;

});

afterEach(() => {

  process.browser = cached; // BETTER

});

```

Ideally its best to use something like [Sinon.js Sandboxing](https://gist.github.com/jgable/fd7fbd0516c849731404), but it is not always possible.

## Install

Does not require any additional dependencies, just itself.

```

npm install global-leaks-finder

```

## Usage

    mocha --check-leaks node_modules/global-leaks-finder/index.js 

## Mocha's check-leaks options

I recommend running in conjunction with Mocha's `check-leaks` flag. It compares against a small list of non-enumerable globals (i.e. `global.newVariable = 'some-value';` would be caught) but would not catch something like `process.execPath = 'GLOBAL LEAK';` which this tool would catch.

## How does it work

It runs a global `beforeEach` and `afterEach`.

For each test it hashes the globals at the start, hashes the globals at the end, and compares the 2 failing if the hash has changed. Hence why it has a hefty performance hit, but hopefully does its job.

## Issues

Please feel free to contact or email me if there are any issues.