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https://github.com/Automattic/expect.js

Minimalistic BDD-style assertions for Node.JS and the browser.
https://github.com/Automattic/expect.js

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Minimalistic BDD-style assertions for Node.JS and the browser.

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README 

        
# Expect



Minimalistic BDD assertion toolkit based on

[should.js](http://github.com/visionmedia/should.js)



```js

expect(window.r).to.be(undefined);

expect({ a: 'b' }).to.eql({ a: 'b' })

expect(5).to.be.a('number');

expect([]).to.be.an('array');

expect(window).not.to.be.an(Image);

```



## Features



- Cross-browser: works on IE6+, Firefox, Safari, Chrome, Opera.

- Compatible with all test frameworks.

- Node.JS ready (`require('expect.js')`).

- Standalone. Single global with no prototype extensions or shims.



## How to use



### Node



Install it with NPM or add it to your `package.json`:



```

$ npm install expect.js

```



Then:



```js

var expect = require('expect.js');

```



### Browser



Expose the `index.js` found at the top level of this repository.



```html



```



## API



**ok**: asserts that the value is _truthy_ or not



```js

expect(1).to.be.ok();

expect(true).to.be.ok();

expect({}).to.be.ok();

expect(0).to.not.be.ok();

```



**be** / **equal**: asserts `===` equality



```js

expect(1).to.be(1)

expect(NaN).not.to.equal(NaN);

expect(1).not.to.be(true)

expect('1').to.not.be(1);

```



**eql**: asserts loose equality that works with objects



```js

expect({ a: 'b' }).to.eql({ a: 'b' });

expect(1).to.eql('1');

```



**a**/**an**: asserts `typeof` with support for `array` type and `instanceof`



```js

// typeof with optional `array`

expect(5).to.be.a('number');

expect([]).to.be.an('array');  // works

expect([]).to.be.an('object'); // works too, since it uses `typeof`



// constructors

expect([]).to.be.an(Array);

expect(tobi).to.be.a(Ferret);

expect(person).to.be.a(Mammal);

```



**match**: asserts `String` regular expression match



```js

expect(program.version).to.match(/[0-9]+\.[0-9]+\.[0-9]+/);

```



**contain**: asserts indexOf for an array or string



```js

expect([1, 2]).to.contain(1);

expect('hello world').to.contain('world');

```



**length**: asserts array `.length`



```js

expect([]).to.have.length(0);

expect([1,2,3]).to.have.length(3);

```



**empty**: asserts that an array is empty or not



```js

expect([]).to.be.empty();

expect({}).to.be.empty();

expect({ length: 0, duck: 'typing' }).to.be.empty();

expect({ my: 'object' }).to.not.be.empty();

expect([1,2,3]).to.not.be.empty();

```



**property**: asserts presence of an own property (and value optionally)



```js

expect(window).to.have.property('expect')

expect(window).to.have.property('expect', expect)

expect({a: 'b'}).to.have.property('a');

```



**key**/**keys**: asserts the presence of a key. Supports the `only` modifier



```js

expect({ a: 'b' }).to.have.key('a');

expect({ a: 'b', c: 'd' }).to.only.have.keys('a', 'c');

expect({ a: 'b', c: 'd' }).to.only.have.keys(['a', 'c']);

expect({ a: 'b', c: 'd' }).to.not.only.have.key('a');

```



**throw**/**throwException**/**throwError**: asserts that the `Function` throws or not when called



```js

expect(fn).to.throw(); // synonym of throwException

expect(fn).to.throwError(); // synonym of throwException

expect(fn).to.throwException(function (e) { // get the exception object

  expect(e).to.be.a(SyntaxError);

});

expect(fn).to.throwException(/matches the exception message/);

expect(fn2).to.not.throwException();

```



**withArgs**: creates anonymous function to call fn with arguments



```js

expect(fn).withArgs(invalid, arg).to.throwException();

expect(fn).withArgs(valid, arg).to.not.throwException();

```



**within**: asserts a number within a range



```js

expect(1).to.be.within(0, Infinity);

```



**greaterThan**/**above**: asserts `>`



```js

expect(3).to.be.above(0);

expect(5).to.be.greaterThan(3);

```



**lessThan**/**below**: asserts `<`



```js

expect(0).to.be.below(3);

expect(1).to.be.lessThan(3);

```



**fail**: explicitly forces failure.



```js

expect().fail()

expect().fail("Custom failure message")

```



## Using with a test framework



For example, if you create a test suite with

[mocha](http://github.com/visionmedia/mocha).



Let's say we wanted to test the following program:



**math.js**



```js

function add (a, b) { return a + b; };

```



Our test file would look like this:



```js

describe('test suite', function () {

  it('should expose a function', function () {

    expect(add).to.be.a('function');

  });



  it('should do math', function () {

    expect(add(1, 3)).to.equal(4);

  });

});

```



If a certain expectation fails, an exception will be raised which gets captured

and shown/processed by the test runner.



## Differences with should.js



- No need for static `should` methods like `should.strictEqual`. For example,

  `expect(obj).to.be(undefined)` works well.

- Some API simplifications / changes.

- API changes related to browser compatibility.



## Running tests



Clone the repository and install the developer dependencies:



```

git clone git://github.com/LearnBoost/expect.js.git expect

cd expect && npm install

```



### Node



`make test`



### Browser



`make test-browser`



and point your browser(s) to `http://localhost:3000/test/`



## Credits



(The MIT License)



Copyright (c) 2011 Guillermo Rauch <[email protected]>



Permission is hereby granted, free of charge, to any person obtaining

a copy of this software and associated documentation files (the

'Software'), to deal in the Software without restriction, including

without limitation the rights to use, copy, modify, merge, publish,

distribute, sublicense, and/or sell copies of the Software, and to

permit persons to whom the Software is furnished to do so, subject to

the following conditions:



The above copyright notice and this permission notice shall be

included in all copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,

EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY

CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,

TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE

SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.



### 3rd-party



Heavily borrows from [should.js](http://github.com/visionmedia/should.js) by TJ

Holowaychuck - MIT.