source: Dev/trunk/node_modules/should/Readme.md @ 484

# should.js

_should_ is an expressive, readable, test framework agnostic, assertion library for [node](http://nodejs.org).

It extends the Object prototype with a single non-enumerable getter that allows you to express how that object should behave.

## Example
```javascript
var should = require('should');

var user = {
    name: 'tj'
  , pets: ['tobi', 'loki', 'jane', 'bandit']
};

user.should.have.property('name', 'tj');
user.should.have.property('pets').with.lengthOf(4);

// or without Object.prototype, for guys how did Object.create(null)
should(user).have.property('name', 'tj');
should(true).ok;

someAsyncTask(foo, function(err, result){
  should.not.exist(err);
  should.exist(result);
  result.bar.should.equal(foo);
});
```
## Installation

    $ npm install should --save-dev

## In browser

If you want to use _should_ in browser, use version that is in root of repository. It is build with browserify (see [Makefile](https://github.com/visionmedia/should.js/blob/master/Makefile) about how it is build). To build fresh version:

```bash
# you should have browserify
npm install -g browserify
make browser
```

## chaining assertions

Every assertion will return a should.js-wraped Object, so assertions can be chained. For example:

```js
user.should.be.an.instanceOf(Object).and.have.property('name', 'tj');
user.pets.should.be.instanceof(Array).and.have.lengthOf(4);
```

All assertions return themselves but not `property` and `ownProperty`. They two would return the property value.

for example if a property is volatile we can first assert property existence:
```javascript
// `user.should.have.property('pets')` returned `should(user.pets)` but not `should(user)`
user.should.have.property('pets').with.lengthOf(4)
```
which is essentially equivalent to below, however the property may not exist:
```javascript
user.pets.should.have.lengthOf(4)
```

our dummy getters such as _a_, _an_, _be_, _of_ and _have_ make tests more readable while the getters _and_ and _with_ helps express chaining:
```javascript
user.should.be.an.instanceOf(Object).and.have.property('name', 'tj')
user.should.have.property('pets').with.a.lengthOf(4)
```
Those getters don't have any actual effect, just for readability.

## static

For some rare cases should can be used statically, without `Object.prototype`.
It can be replacement for node assert module (and it uses the same `AssertionError`):

```javascript
assert.fail(actual, expected, message, operator) // just write wrong should assertion
assert(value, message), assert.ok(value, [message]) // should(value).ok
assert.equal(actual, expected, [message]) // should(actual).eql(expected, [message])
assert.notEqual(actual, expected, [message]) // should(actual).not.eql(expected, [message])
assert.deepEqual(actual, expected, [message]) // should(actual).eql(expected, [message])
assert.notDeepEqual(actual, expected, [message]) // should(actual).not.eql(expected, [message])
assert.strictEqual(actual, expected, [message]) // should(actual).equal(expected, [message])
assert.notStrictEqual(actual, expected, [message]) // should(actual).not.equal(expected, [message])
assert.throws(block, [error], [message]) // should(block).throw([error])
assert.doesNotThrow(block, [message]) // should(block).not.throw([error])
assert.ifError(value) // should(value).Error (to check if it is error) or should(value).not.ok (to check that it is falsy)
```

## ok

Assert truthfulness:
```javascript
true.should.be.ok
'yay'.should.be.ok
(1).should.be.ok
```
or negated:
```javascript
false.should.not.be.ok
''.should.not.be.ok
(0).should.not.be.ok
```
## true

Assert === true:
```javascript
true.should.be.true
'1'.should.not.be.true
```
## false

Assert === false:
```javascript
false.should.be.false
(0).should.not.be.false
```
## arguments

Assert `Arguments`:
```javascript
var args = (function(){ return arguments; })(1,2,3);
args.should.be.arguments;
[].should.not.be.arguments;
```
## empty

Asserts that given object is empty
```javascript
[].should.be.empty
''.should.be.empty
({}).should.be.empty
(function() {
  arguments.should.be.empty;
})()
```
## eql

equality:
```javascript
({ foo: 'bar' }).should.eql({ foo: 'bar' })
[1,2,3].should.eql([1,2,3])
```
## equal and exactly

strict equality:
```javascript
should.strictEqual(undefined, value)
should.strictEqual(false, value)
(4).should.equal(4)
'test'.should.equal('test')
[1,2,3].should.not.equal([1,2,3])
(4).should.be.exactly(4)
```
## within

Assert inclusive numeric range:
```javascript
user.age.should.be.within(5, 50)
```
## approximately

Assert floating point number:
```javascript
(99.99).should.be.approximately(100, 0.1);
```
## type

Assert __typeof__:
```javascript
user.should.be.type('object')
'test'.should.be.type('string')
```
## instanceof and instanceOf

Assert __instanceof__ or __instanceOf__:
```javascript
user.should.be.an.instanceof(User)
[].should.be.an.instanceOf(Array)
```
## above

Assert numeric value above the given value:
```javascript
user.age.should.be.above(5)
user.age.should.not.be.above(100)
```
## below

Assert numeric value below the given value:
```javascript
user.age.should.be.below(100)
user.age.should.not.be.below(5)
```
## NaN

Assert numeric valus is NaN:
```javascript
(undefined + 0).should.be.NaN;
```
## Infinity

Assert numeric valus is Infinity:
```javascript
(1/0).should.be.Infinity;
```
## match

Assert regexp match:
```javascript
username.should.match(/^\w+$/)
```
## length

Assert _length_ property exists and has a value of the given number:
```javascript
user.pets.should.have.length(5)
user.pets.should.have.a.lengthOf(5)
({ length: 10}).should.have.length(10);
```
Aliases: _lengthOf_

## property

Assert property exists and has optional value:
```javascript
user.should.have.property('name')
user.should.have.property('age', 15)
user.should.not.have.property('rawr')
user.should.not.have.property('age', 0)
```

## properties

Assert given properties exists:
```javascript
user.should.have.properties('name', 'age');
user.should.have.properties(['name', 'age']);
```
## ownProperty

Assert own property (on the immediate object):
```javascript
({ foo: 'bar' }).should.have.ownProperty('foo')
```
## status(code)

 Asserts that `.statusCode` is `code`:
```javascript
res.should.have.status(200);
```
## header(field[, value])

 Asserts that a `.headers` object with `field` and optional `value` are present:
```javascript
res.should.have.header('content-length');
res.should.have.header('Content-Length', '123');
res.should.have.header('content-length', '123');
```
## json

  Assert that Content-Type is "application/json; charset=utf-8"
```javascript
res.should.be.json
```
## html

  Assert that Content-Type is "text/html; charset=utf-8"
```javascript
res.should.be.html
```

## include(obj) or contain(obj)

Assert that the given `obj` is present via `indexOf()`, so this works for strings, arrays, or custom objects implementing indexOf. Also it can assert if given object will have some sub-object.

Assert array value:
```javascript
[1,2,3].should.include(3)
[1,2,3].should.include(2)
[1,2,3].should.not.include(4)
```
Assert substring:
```javascript
'foo bar baz'.should.include('foo')
'foo bar baz'.should.include('bar')
'foo bar baz'.should.include('baz')
'foo bar baz'.should.not.include('FOO')
```
Assert object includes another object:
```javascript
var tobi = { name: 'Tobi', age: 1 };
var jane = { name: 'Jane', age: 5 };
var user = { name: 'TJ', pet: tobi };

user.should.include({ pet: tobi });
user.should.include({ pet: tobi, name: 'TJ' });
user.should.not.include({ pet: jane });
user.should.not.include({ name: 'Someone' });
```
## includeEql(obj)

Assert that an object equal to the given `obj` is present in an Array:
```javascript
[[1],[2],[3]].should.includeEql([3])
[[1],[2],[3]].should.includeEql([2])
[[1],[2],[3]].should.not.includeEql([4])
```
## throw()

Assert an exception is thrown:

```js
(function(){
  throw new Error('fail');
}).should.throw();
```

Assert an exception is not thrown:

```js
(function(){

}).should.not.throw();
```
Assert exception message matches string:

```js
(function(){
  throw new Error('fail');
}).should.throw('fail');
```

Assert exepection message matches regexp:

```js
(function(){
  throw new Error('failed to foo');
}).should.throw(/^fail/);
```

## throwError()

An alias of `throw`, its purpose is to be an option for those who run
[jshint](https://github.com/jshint/node-jshint/) in strict mode.

```js
(function(){
  throw new Error('failed to baz');
}).should.throwError(/^fail.*/);
```

## startWith(str)

Assert that string starts with `str`.

```javascript
'foobar'.should.startWith('foo')
'foobar'.should.not.startWith('bar')
```
## endWith(str)

Assert that string ends with `str`.

```javascript
'foobar'.should.endWith('bar')
'foobar'.should.not.endWith('foo')
```

## keys

Assert own object keys, which must match _exactly_,
and will fail if you omit a key or two:

    var obj = { foo: 'bar', baz: 'raz' };
    obj.should.have.keys('foo', 'baz');
    obj.should.have.keys(['foo', 'baz']);

## type assertions

```javascript
({}).should.be.an.Object;
(1).should.be.an.Number;
[].should.be.an.Array;
(true).should.be.a.Boolean;
''.should.be.a.String;
```

## Optional Error description

As it can often be difficult to ascertain exactly where failed assertions are coming from in your tests, an optional description parameter can be passed to several should matchers. The description will follow the failed assertion in the error:

    (1).should.eql(0, 'some useful description')

    AssertionError: expected 1 to equal 0 | some useful description
      at Object.eql (/Users/swift/code/should.js/node_modules/should/lib/should.js:280:10)
      ...

The methods that support this optional description are: `eql`, `equal`, `within`, `a`, `instanceof`, `above`, `below`, `match`, `length`, `property`, `ownProperty`, `include`, and `includeEql`.

## Mocha example

For example you can use should with the [Mocha test framework](http://visionmedia.github.io/mocha/) by simply including it:

```javascript
var should = require('should');
var mylib = require('mylib');


describe('mylib', function () {
  it('should have a version with the format #.#.#', function() {
    lib.version.should.match(/^\d+\.\d+\.\d+$/);
  }
});
```

## Running tests

To run the tests for _should_ simply run:

    $ make test

## OMG IT EXTENDS OBJECT???!?!@

Yes, yes it does, with a single getter _should_, and no it won't break your code, because it does this **properly** with a non-enumerable property.

## License

(The MIT License)

Copyright (c) 2010-2011 TJ Holowaychuk <tj@vision-media.ca>

Copyright (c) 2011 Aseem Kishore <aseem.kishore@gmail.com>

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.