frankthelen/chai-quantifiers

# chai-quantifiers

Array quantifier assertions for [Chai](http://chaijs.com/) assertion library.

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## Install

```bash
npm install --save-dev chai chai-quantifiers
```

## Usage

There are three assertions available, applicable to arrays.

* containAll -- Asserts that all array items are true in respect to a predicate.
* containOne -- Asserts that at least one array item is true in respect to a predicate.
* containExactlyOne -- Asserts that exactly one array item is true in respect to a predicate.

A quick example:

```javascript
const chai = require('chai');
const chaiQuantifiers = require('chai-quantifiers');

chai.use(chaiQuantifiers);

const { expect } = chai;

describe('chai-quantifiers', () => {
  it('containAll should be true if all items are true', () => {
    expect([0, 1, 2, 3]).to.containAll(item => item < 4);
  });
  it('containOne should be true if at least one item is true', () => {
    expect([0, 1, 2, 3]).to.containOne(item => item >= 2);
  });
  it('containExactlyOne should be true if exactly one item is true', () => {
    expect([0, 1, 2, 3]).to.containExactlyOne(item => item === 2);
  });
});
```

This module also includes types for *TypeScript*.